Military people are retiring at too young an age and at too great a cost to the Treasury, according to a heavily supported view within President Carter's advisory panel.

The majority of the nine-member commission President Carter appointed in June -- and said would shape his recommendations to Congress -- has indicated that military people should no longer be able to retire after 20 years' service at half pay, as they can now.

Instead, the majority is leaning toward requiring service men and women to reach age 55 and serve at least 30 years to qualify for full retirement. Shorter service would be compensated on a reduced basis as in civilian retirement programs.

Retirement pay is eating up a growing share of the Pentagon budget, with the cost thought likely to reach $10 billion this coming fiscal year and $37 billion for the year 2000 if changes are not made.

Military leaders have been warning the President's Commission on Military Compensation against making any changes in the retirement system for fear of spreading disillusionment in the career force.

But commission members have recently gone beyond taking testimony and have started expressing their dismay with the military retirement structure and its impact.

Walter H. Page, president of the Morgan Guaranty Trust Co., who is on the commission's retirement subcommittee, said the current system amounts to "inhumanity" because it consists of "holding out a bribe" to a serviceman to make him "do something which he really hates like hell."

Page expressed that view at a commission meeting in Hartford, Conn., last week. The transcript became available yesterday.

"When I see people who don't really get any satisfaction out of their jobs" but only stay in them for retirement benefits, "I know you have got an inefficient person," Page said.

Commission member Jane C. Pfeiffer, an IBM management specialist, said at the meeting that today's young service people seem to want to be financially rewarded for jobs well done as they go along rather than wait for a generous retirement at the end of their careers. This aspect of the military retirement system, she said "bothers me greatly."

John H. Filer, a third civilian commission member, who is board chairman of Aetna Life and Casualty, said it would be "almost impossible" to keep the current military retirement system in force.

Thomas Ehrlich, president of Legal Service Corp., said he favored setting a minimum age for military officers to retire, "like 55." Commission chairman Charles J. Zwick, president of Southeast Banking Corp., sent word to the Hartford meeting, which he did not attend, that he would be "comfortable" with requiring 30 years' military service to qualify for full retirement.

The remarks at the Jan. 5 meeting were the first time the commissioners indicated how they stood on one military retirement issue after assessing months of testimony. Five of the nine commissioners have suggested reforms.

Two panel members are retired Army generals. William E. DePuy and Benjamin O. Davis Jr. Both have been warning against scrapping the incentives embodied in the current retirement system, although DePuy said at the Hartford meeting that he could go along with raising the retirement age for officers.

However, DePuy said that it would be risky to alter retirement now available to enlisted people. "We are getting more quality sergeants and petty officers per dollar under the current system than I suspect we will get under any other system," he said.

The military retirement program, DePuy continued, "is an instrument for persuading soldiers and petty officers to take assignments to unpleasant places without their families, because if they don't take it, they lose the 20 year retirement. You can say it is ruthless. I say it is effective."

Changing the system to one where retirement would be vested like civilian programs would mean that "the minute somebody gets assigned to a disagreeable spot, why he is likely to pick up his equity and walk out the door," DePuy said.

The commission is scheduled to report to Defense Secretary Harold Brown and President Carter by March 15 so that recommendations can be used in drafting military retirement legislation for Congress.

Congress has failed to act on proposed revisions of the military retirement system in the past and may refuse to do so again in this election year unless the President exerts pressure.

The presidential commission is weighing whether to recommend exempting everyone now in the military from any new retirement system, exempting only those with more than four years' service, or exempting only those with 10 or more years' service.