The Carter administration will revive - with what it hopes is a more politically palatable formula - a Nixon administration plan that would set up a separate pay, selection and tenure system for many of the government's top career executives.

Although still in the planning stage, the idea is to create a cadre of mobile executives in Grades 16, 17 and 18 (pay range $39,629 to $47,500) who could be assigned to limited and renewable tours of duty and serve at the pleasure of the agency head.

A somewhat smilar proposal, called the Federal Executive Service, was put forth during the Nixon years. It was shot down in Congress because of opposition from the career bureaucracy and fear of congressional Democrats that it could be used to politicize further the top echelons of the government's career executive ranks.

Main objection to the FES was a provision for a 3-to 5-year renewable contracts for the executives. If the agency head choose not to renew a contract the supergrade level employee could be removed from that job and given the option of early retirement or transfer to a similar pay level elsewhere.

Democrats in Congress claimed the contracts could be used as a device by managers to eliminate or reduce the number of career supregraders, or put them in less influential jobs. They could be replaced, so the arguments went, by more politically suitable executives from among the career-political cadre mixed proposed by the FES. At any rate, the plan fizzled.

Now, however, something like it is about to resurface, although officials involved in the hush-hush planning say it will be different from the Nixon administration proposal.

Among other things, insiders say, the word "contract" will not be uttered or used since that has a terminal implication that makes career executives nervous - maybe for good reason.

Planners hoped the revamped, resurrected executive proposal will have sufficient guarantees to give new Carter administration officials added numbers of new, trusted executives they can call on without alarming old-line careerists.

Whatever the final outcome, the fact is that Democrats now control the White House and the Congress. So it is unlikely that the new executive plan will run into arguments - with enough votes to block it - that it is too political. And since they are likely to get what they want, it is all the more important that the Carter administration be sure it wants what it gets.