Virginia corrections chief Allyn R. Sielaff, who is credited with bringing sweeping changes to the state's prison system, announced yesterday that he is quitting to head a juvenile court program in Ohio.

Sielaff, a 54-year-old lawyer who took charge of the Virginia Department of Corrections as it was reeling from the largest death row breakout in U.S. history, won the support of both conservative state legislators and liberal advocates of prison reform.

His decision to resign from the $62,000-a-year position, disclosed in Richmond by Gov. Charles S. Robb, surprised colleagues as well as state officials. Sielaff, who has headed prison systems in Pennsylvania, Illinois and Wisconsin, said he will return to Cleveland as administrator of the juvenile court services for Cuyahoga County at an undisclosed salary.

Sielaff said he had "every single indication" that he would be reappointed by Democratic Gov.-elect Gerald L. Baliles, who takes office Jan. 11, but wanted to work with juvenile offenders.

"It's a job I wanted to do," said Sielaff in a telephone interview from his Richmond home. "At this stage I'm not looking for a step up or more money. I've headed corrections systems in several states and had the biggest challenge anybody could have in Virginia. I'm interested in my own personal and professional satisfaction."

"I regret that he has decided not to remain for a longer period of time, but I understand and respect his reasoning" said Robb, whose administration had been more successful in dealing with prison problems under Sielaff than either of his two predecessors.

Robb appointed Sielaff's deputy, Edward W. Murray, 42, to serve as acting director until the end of his administration. Murray, who is currently deputy director of adult institutions, is a 15-year veteran of the Corrections Department.

The court system Sielaff will head is the same one in which he began his corrections career working in a juvenile detention home at age 19. He said he was selected from among 130 applicants for the new position. Although the county's juvenile system is the largest in Ohio, its 500-member staff is far smaller than the 8,000-employe department Sielaff has directed since November 1984.

The position as court administrator and chief of legal services, which Sielaff assumes Jan. 2, could lead to other positions in the Ohio court system, including a judgeship, officials said.

Robb hired the aggressive and controversial Sielaff to carry out his mandate for massive changes in the state's troubled prison system, which he has declared the number one crisis of his administration.

Sielaff, who was called a "breath of fresh air" by Alvin Bronstein of the American Civil Liberties Union, one of the Virginia system's harshest critics, ordered major changes in the prisons within days of taking office. He said he leaves without having completed everything he set out to do, but having done "more than anybody else has accomplished in a year's period of time here."

The corrections chief said he thinks his greatest accomplishment is that "people in the department feel better about themselves and the public feels better about the department."

"Turning around Mecklenburg," the prison in southern Virginia that was the scene of the death row escape, also ranks high on his own list of achievements, he said. The prisons system's public image and employe morale collapsed in the aftermath of the 1984 escape of six death row inmates from what had been considered the state's highest security prison.

"For over a year, Allyn Sielaff has handled with distinction one of the most difficult jobs in state government," Robb said in a statement yesterday.

Chris Bridge, press secretary to Baliles, said the governor-elect shared Robb's regret with Sielaff's decision to resign. "He [Baliles] was impressed with his accomplishments and management and he would have given strong consideration to reappointing him," Bridge said.