Secretary of Defense Caspar W. Weinberger announced yesterday that a formal board of inquiry will be convened to investigate "all . . . circumstances" surrounding the suicide attack that killed more than 225 U.S. Marines in the multinational peace-keeping force in Lebanon a week ago.

Pentagon officials said the board is expected to probe, among other things, whether adequate security precautions were in effect at the Marine headquarters unit when a truck laden with more than a ton of explosives was driven into the building at Beirut International Airport and blown up, flattening the structure.

The investigation will be headed by retired Adm. Robert L. Long, former commander of Navy forces in the Pacific, and was recommended by Gen. Paul X. Kelley, the Marine commandant, who had said earlier that he was "totally satisfied" with security procedures in Beirut.

The announcement came as Pentagon officials said 200 additional Marines were flying from Camp Lejeune, N.C., to Beirut to reinforce the 1,600 now on the ground there. A spokesman said the rifle company will provide security for the Marines still excavating the rubble.

Meanwhile, officials said several means of retaliation are under study against Iran, which the administration strongly suspects was behind the attack. President Reagan privately told a Jewish group last Wednesday that the evidence is "sufficient" to suggest that the attack was carried out by Iranian terrorists with help from Syria, according to a White House official. Administration officials said military as well as economic and diplomatic forms of retaliation are under consideration but no choices have been made.

Officials also said yesterday that Reagan is considering the appointment of Alfred L. Atherton Jr., departing ambassador to Egypt, to work "in a supporting role" to whomever is next named special Middle East envoy. The leading candidate for the envoy's post, officials have said, is former defense secretary Donald H. Rumsfeld.

And in still another Mideast development, the Republican-controlled Senate voted to prohibit spending on a Reagan administration plan to train and equip a Jordanian rapid deployment force unless the secrecy-cloaked project is openly approved by Congress. The Senate language, proposed by Sen. Daniel Patrick Moynihan (D-N.Y.) and approved on a voice vote, would override a secret section of the 1984 defense authorization bill in which Congress authorized more than $220 million for the project.

In the aftermath of the bombing, there have been demands in Congress for an investigation into the security precautions in effect at the building. The driver of the small truck passed several Marine guards before detonating the explosives in the building's lobby.

Kelley, the Marine commandant, said in Beirut last week, "I think we had very adequate security measures. One has to realize if you have a determined individual who is willing to give up his life, chances are he's going to get through and do that."

Kelley has since returned from Beirut and reported to Reagan on the bombing attack. In his nationally televised speech Thursday night, the president downplayed the question of security at the Marine headquarters. He noted that the truck had "nothing in its appearance to suggest it was any different than the trucks or cars that were normally seen on and around the airport."

Reagan said that, although the truck carried some 2,000 pounds of explosives, "there was no way our Marine guards could know this." He said their first warning that something was wrong came when the truck crashed through a series of barriers and a chain link fence. "The guards opened fire, but it was too late."

Reagan vowed in his address that "those who directed this atrocity must be dealt justice. They will be."

Officials said the retaliatory alternatives under study range from having the Lebanese close the Iranian embassy in Beirut to staging a possible commando raid into the Baalbek area of eastern Lebanon where a radical Lebanese group and some Iranian revolutionary guards thought to have had a role in the bombing are known to be based.

Reagan, in remarks to the Jewish group Wednesday that were not made public at the time, said of the bombing attack: "I think the evidence that I have is sufficient that this last horrendous act involved Iranian terrorists, and they were facilitated in their entry and in the provisions of the munitions by the Syrians."

The Jordanian rapid deployment force, which Moynihan estimated will ultimately cost $700 million, was secretly proposed by the administration to help protect friendly Arab countries against attacks or coups.

Moynihan's proposal, which the Senate Republican leadership did not attempt to block, would bar spending for the Jordanian force "unless such expenditure is expressly authorized and funds appropriated by Congress in an unclassified manner."

Moynihan's prohibition was attached to a debt ceiling bill that may ultimately be stripped of all such legislative "riders." But Moynihan told a reporter he intends to keep attaching the provision to available legislation until it passes.

He also said the "practical effect will be to kill the project" because Congress would never approve it openly.

But in brief debate over the proposal, Moynihan also ridiculed the notion that the controversial plan, which was kept secret until it was disclosed on Israeli radio and then reported in U.S. newspapers this month, could be kept quiet.

"You could dress up a light armored vehicle to look like a camel, but not very successfully," said Moynihan. "They do not walk like camels. They will move differently from camels. I don't know how you disguise an F16 as a camel. I have never seen a camel fly but, then, I do not want to underestimate the ingenuity of our military planners."