The U.S. attorney's office in Alexandria, which has suffered from charges of disorganization, poor leadership and strained relations with local attorneys, is about to get a new leader who hopes to change all that.

Reorganizing the office "is going to be a monumental task, but I intend to do it," said Arlington County Commonwealth's Attorney Henry E. Hudson, who President Reagan has named to head the U.S. attorney's office.

Hudson's nomination as top federal prosecutor for the Eastern District of Virginia was approved last week by the Senate Judiciary Committee, and he is expected to be in office by June.

"My goal is to create a U.S. attorney's office with a national reputation for quality prosecutions, and being firm and fair in the decisions we make," said the 38-year-old Republican. "I have a very structured style of management . . . and I believe in firm administrative control."

Hudson, who has been in the Alexandria office before, as an assistant federal prosecutor for two years in the late 1970s, will use prosecutorial and administrative skills in the $70,500-a-year job, which has been the focus of fire from lawyers, politicians and judges in Virginia.

The office this month suffered two highly visible defeats. First, a jury acquitted former Army counterintelligence specialist Richard Craig Smith of espionage, one of the government's few losses in recent prosecutions of alleged spies.

Then, after a three-day trial in which the prosecution's principal witness admitted giving erroneous testimony to a grand jury, Alexandria Police Chief Charles T. Strobel was found not guilty of perjury and obstruction of justice.

Strobel's indictment, termed "unnecessary, unwarranted, and unworthy of the government" by his defense counsel, was widely criticized by city officials, and the investigation that preceded it strained relations between the federal prosecutor's office and state officials who had cleared Strobel a year ago after a similiar probe.

Several defense attorneys said in interviews they have been frustrated by some of the office's lawyers, who, they say, have been overly tough in plea bargaining, discourteous, and at times unfaithful to promises.

"I hope he will bring the place more under control," said Alexandria lawyer Marvin D. Miller, "and increase its reputation for professionalism above its present level . . . because its reputation is not what it was in the past."

Elsie L. Munsell, who left the office in January to join the Navy's office of general counsel, was once thought likely to become the first woman federal judge in Virginia. But she rarely appeared in court, opting to spend most of her time in administrative duties in the sprawling district that includes Richmond and Norfolk.

While personally liked by many, Munsell was faulted for delegating too much authority, leaving the impression that some of her youthful assistants were "out of control," as several lawyers put it. Although hard-working, Munsell failed to put her personal imprint on the office, which has a staff of more than 70, nearly half of them lawyers, some lawyers said.

"I think I and the team of people I worked with were able to achieve some good things while I was in office," Munsell said yesterday. "I attribute a lot of the hard words for people on my staff to the heat of battle" and differences on "how to handle cases, especially drug cases."

Munsell oversaw some major convictions, including that of Portsmouth Police Chief E. Ronald Boone on charges of perjury, mail fraud and obstruction of justice, and more than 40 people involved in multimillion-dollar drug rings in Northern Virginia and in Richmond in 1984 and 1985.

At the same time her staff came under public fire from the bench at least four times. District Judge Robert R. Merhige Jr. criticized the office for a plea bargain with Hartz Mountain Corp. in 1984, and the 4th Circuit Court of Appeals that year faulted her prosecutors for "equivocation in making factual representations to defense counsel" in a health insurance fraud case.

Last year U.S. District Judge James C. Cacheris scolded two of her attorneys in Alexandria for allowing an indictment to be returned against a man who supposedly wrote the judge a threatening letter. Cacheris said he had told the prosecutors that he wanted no action taken against the letter-writer.

In the fourth case, Chief District Judge Albert V. Bryan Jr. criticized Munsell's office for its "no harm done" attitude after a prosecutor looked at sealed documents during a grand jury investigation.

If the Strobel case embarrassed the office in Northern Virginia, then its Norfolk office sustained an equally embarrassing defeat last year when a jury there acquitted two Portsmouth politicians, state Sen. John S. Joannou and former state senator Willard J. Moody, of mail fraud and conspiracy charges in an alleged ticket-fixing scheme.

Hudson said in an interview he was aware of "comments afloat in the legal community" about the office, but he said he believes that he can resolve the difficulties. "I'm a person who believes in close monitoring and knowing what everyone on my staff is doing," he said.

He refused to discuss specific changes, saying he wants to talk with the staff, local attorneys and judges before he moves to get it "functioning to my personal satisfaction." Changes "will be made gradually . . . . There are a lot of excellent lawyers on the staff right now," he said.

Hudson, who wears his sandy brown hair closely cropped and has a Cheshire cat-like grin, is leaving an elective job he has held since 1980 in which he oversaw a staff of nine lawyers and was the youngest local prosecutor in the Washington area. He attended night classes at American University Law School to get his degree, and in Arlington he earned a reputation as a tough, relentess and rigid prosecutor who reduced plea bargains, increased prison terms for burglars and cracked down on massage parlors, adult bookstores and drugs.

His federal position will not be "so freewheeling as this one," he said. He will try some cases himself.

"There are certain types of cases where the full dignity of the U.S. attorney's office is on the line and I want to be in court," he said. "To be able to oversee experienced trial lawyers, you have to be a trial lawyer yourself."

He declined to discuss the Smith espionage case, saying he "didn't follow" it, and he refused to talk about the Strobel prosecution. "Charlie Strobel is a friend of mine. I'm not going to discuss it," he said.

He suggested that "some improvement is necessary" in the relationship between the office and Virginia law enforcement offices, a relationship that was strained by the Strobel case.

He also wants to improve the office's reputation among lawyers. "Whatever representations are made by the U.S. attorney's office, they will be backed by my personal integrity," he said.

People who come to see him "may have to wait in line, but I'm available to talk to them . . . and I return every phone call I get that same day. I expect my staff to do the same."

Some lawyers have expressed concern that Hudson, who for the past year has chaired the controversial Attorney General's Commission on Pornography, may give too much priority to that issue. Hudson declined to talk about the matter, complaining that his positions on pornography have been misunderstood.

Hudson says he has matured in his job, or "grown up," as he put it. He said he has moved away from a common mind-set among new prosecutors of seeing themselves "first as supercops."

"We are lawyers first.