One of the foremost critics of SALT II suggested four amendments yesterday to the proposed strategic arms limitation treaty and said its ourtright rejection "would not be the end of the world."

Paul Nitze, a former deputy secretary of defense, said he thought the Soviets might accept at least some of the changes.

But an administration spokesman, Hodding Carter, said no changes were necessary, and reiterated Secretary of State Cyrus Vancehs statements that substantive amendments risked killing the treaty.

Senate votes on amendments to the proposed treaty are likely to be key battles in the ratification struggle. Nitze is one of the first major critics to propose a specific list of changes.

Nitze's proposals, made public at a breakfast meeting with reporters, are:

A stipulation of the right to adopt the "shell game" system of basing missiles. The United States would dig thousands of dummy holes and move its missiles secretly from one to another, to protect them from increasingly accurate mulitple-warhead Soviet missiles by giving the Soviets too many targets to cover.

The administration says the treaty as written would allow a shell game deployment, which it now has under consideraton. It says the treaty would only require it to devise a way for the Soviets to spot-check some holes and satisfy themselves that the United States was not actually deploying more missiles than the treaty allows.

Nitze maintains, however, that the treaty is amibiguous about whether the shell game would be allowed. He says rules prohibiting concealment of launchers would give the Soviest a strong case to argue against the shell game.

An amendment to equalize and reduce the number of heavy missiles allowed each side.

As the treaty stands, the Soviets would be allowed to keep their 308 "heavy missile launchers" which contain mammoth SS9 and SS18 rockets, and new missiles for either side would be limited to a size about half that of the SS18. Since the United States has no heavy missiles, this would effectively preclude it from developing any.

Administration spokesmen justify this by noting that the United States has never wanted huge missiles, because it has always been able to build smaller, more accurate ones.

A verification amendment, to make certain that the Soviets are not able to encode vital data from their missile tests.

The administration says it is satisfied that the treaty will prevent the Soviets from encoding data needed for verification and that the United States would be able to detect cheating.

An amendment to include the Soviet Backfire bomber on the list of strategic weapons, of which each side is permitted a total of 2,250.

Backfire is apparently designed for medium-range missions in Europe and Asia, but it could reach the United States if it flew at slow speeds and landed in Cuba. The Carter administration accepted in 1977 the Soviet contention that Backfire was not a strategic weapon. It will be covered in a separate letter, under which Soviet President Leonid Brezhnev will promise not to increase the capability of the plane or its production rate of 30 per year.