The choice of former senator John G. Tower to be strategic arms negotiator came as a surprise Friday to Tower and nearly everybody else, except the top administration officials who picked him. Insiders said yesterday that the Texas Republican was secretly "the preeminent candidate" of top officials all along.

One reason the policymakers kept secret Tower's potential role in the forthcoming U.S.-Soviet negotiations on nuclear and space arms was to avoid alerting and alarming friends of retired general Edward L. Rowny, whom Tower is to replace as chief negotiator on long-range nuclear arms.

The stealth was so successful that Rowny is described by friends as taken completely by surprise when informed of the switch, and of his appointment to a vague advisory post, by Secretary of State George P. Shultz about 1 p.m. Friday. About 45 minutes later Rowny found himself in the Oval Office, being asked by President Reagan to become a "special adviser" with access to the negotiators' cable traffic and participation in high-level White House meetings on arms control.

Asked about Rowny's reaction, a close friend replied: "He was crushed."

After speaking to the former strategic arms negotiator late Friday, Rowny's aides were uncertain whether he would agree to remain in the administration in the advisory role, but Rowny said in a telephone interview yesterday, "I agreed to serve."

As evidence that Rowny is still on the team, a White House official said he is expected to be present Tuesday morning when Reagan meets for the first time with his new group of arms control negotiators and advisers.

The Tuesday morning meeting, billed by the White House as Reagan's first order of business in his second term, is to include Shultz, Secretary of Defense Caspar W. Weinberger and national security affairs adviser Robert C. McFarlane, the ones responsible for proposing Tower.

Special arms control adviser Paul H. Nitze, who is reported to have played a key behind-the-scenes role in this and other arms decisions, is expected to be present, along with Rowny, Vice President Bush and Director Kenneth L. Adelman of the Arms Control and Disarmament Agency.

The costars of the show, under Reagan's direction, are to be the three new faces comprising the 1985 team: space arms negotiator and delegation chief Max M. Kampelman, medium-range arms negotiator Maynard W. Glitman and strategic arms negotiator Tower.

During 24 years in the Senate, Tower, 59, developed close ties with policymakers at or near the top of a variety of U.S. agencies that often have been at odds on arms control.

Tower was in effect McFarlane's boss in 1978-80 when the future White House security adviser was a staff member on the Republican side of the Senate Armed Services Committee and Tower was the senior Republican.

Other administration officials who used to be committee staff aides under Tower include Ronald F. Lehman, arms control specialist on the National Security Council staff, and Frank J. Gaffney, arms control deputy to Assistant Secretary of Defense Richard N. Perle.

Tower's former administrative assistant, William L. Ball, was recently recruited by Shultz to be the State Department's chief of congressional relations.

As chairman of the Senate Armed Services Committee in Reagan's first term, Tower was among the most consistent and important congressional supporters of Weinberger and of Reagan defense programs.

On the State Department side, Tower was sounded out as a possible ambassador to West Germany in early January prior to the U.S.-Soviet meeting in Geneva that created a three-part structure for new arms negotiations.

Despite some recent rumors that he might be asked to play a role in the arms negotiations, Tower said yesterday, he was not sounded out about the negotiating job until Shultz made the offer in a 9:30 a.m. Friday State Department meeting. Shultz had arranged the appointment the day before without indicating its purpose.

Administration officials said Shultz felt some concern about whether Tower would accept, in view of "the many other options" available to the former senator, including the embassy in Bonn and a variety of more lucrative and probably less demanding jobs in private life.

Tower said that, after serving in the Senate since 1961, "I just felt I'd been there long enough, and I had some frustrations with the Senate."

He said that he had been looking forward to private life, "the freedom it would give me, and the privacy," but that these considerations were secondary when asked on behalf of the president to undertake an important post, even a mere two weeks after retiring.

In the Senate, Tower was considered a leading defense "hawk" and no fan of concessions to the Soviets.

He and the late Democratic senator Henry M. Jackson of Washington led the unsuccessful 1977 fight against President Jimmy Carter's nomination of Paul C. Warnke to be arms control negotiator with the Soviets and the successful 1979 battle against ratification of the SALT II treaty.

On the other hand, Tower backed the 1972 Anti-Ballistic Missile (ABM) treaty and SALT I interim agreement.

Tower has made some rough statements about the Soviet Union in his political career, including accusations that they do not negotiate in good faith, but he said he does not believe that this will impede his role as a negotiator. "They've said some pretty rough things about us . . . . what's been said in the past will not have, really, that much relevance in the negotiations because I think each nation will be considering its national interests," Tower said.

Kampelman, 64, was reported yesterday to have been an early Shultz choice, in part because of the Washington attorney's strong performance as negotiator with the Soviets and others in 1980-83 Madrid talks on European security. Another part of Kampelman's appeal was said to be his standing as a conservative Democrat who was an aide of the late senator and vice president Hubert H. Humphrey and a foreign policy adviser last fall to Democratic presidential candidate Walter F. Mondale.

An administration official said Kampelman was selected as overall administrative chief of the three-part negotiating team because of his experience as head of the Madrid delegation and because the space talks that he will head may involve less detail than the "interconnected" talks on strategic and intermediate-range arms.

Glitman, 51, was deputy head of the negotiating team in the unsuccessful 1981-83 Intermediate-range Nuclear Force (INF) negotiations with the Soviets. He is reported to have been strongly backed by Nitze, who was chief U.S. negotiator at the previous INF talks and Glitman's boss.

Glitman, a career Foreign Service officer, held economic and political posts until the mid-'70s, when he switched to dealing with the North Atlantic military alliance while on loan to the Pentagon and as deputy U.S. representative to NATO.

For more than a year, Glitman has been chief U.S. negotiator in the Vienna talks with the Soviets and others on conventional-force reductions in Europe.