The Reagan administration has eliminated one of the principal anti-tax-shelter provisions of its tax simplification plan, administration sources said yesterday.

Unless last-minute changes are made, the president's revised proposal will not call for taxing limited partnerships with more than 35 members as if they were corporations, as the Treasury Department did in its original version.

The change was suggested initially because the large partnerships -- operating principally in oil, gas and real estate -- have in recent years become widely used tax shelters that, unlike corporations, permit tax benefits to be passed along to each partner.

In the case of real estate in particular, the benefits are substantial because members of the partnership, or syndication, can write off tax losses greater than the amount of cash they have actually invested.

The benefits are less generous for oil and gas, but nonetheless significant. They spring from the fact that, in any partnership, tax losses can be passed through to all investors and written off against income from other sources. As a result, investors in limited partnerships can get substantial benefits even though they do not have a share in management decisions and are not liable for the debts of the partnership.

Corporate stockholders, on the other hand, have limited liability but can't take the tax breaks because they belong to the corporate entity. And members of a general partnership are liable for whatever debt or losses the entity has.

Limited partnership tax shelters have attracted billions of dollars seeking short-run tax benefits. A report by the Ralph Nader-founded Public Citizen earlier this year said that money invested in public tax shelter partnerships rose from $785 million in 1976 to more than $13 billion in 1983. According to Treasury figures, partnerships with more than 35 partners have about 2.7 million members.

"In short, the limited partnership vehicle offers many of the investment and legal characteristics of a corporation, yet under current law is treated for tax purposes as a partnership," says the original Treasury proposal.

The effect of the growth has been to divert funds from investment in the corporate sector to investment in partnerships, while undermining the general tax-law principle that only active investors should be able to take tax losses on their investments, the document says.

The issue was the subject of heavy lobbying at Treasury by real estate, oil and gas and Wall Street firms. Most of them contended that the original Treasury proposal was unfair because it would have permitted large, wealthy investors to continue to be limited partners while those with less money to put up would be excluded.

"It is difficult to understand why the proposal would permit 35 millionaires to conduct a multimillion-dollar business as a limited partnership, whereas 350 small investors who wish to conduct the same enterprise must either use a corporate vehicle or face the additional business risk . . . as general partners," according to a report prepared for the Oil Investment Institute. It was written by G. David Glickman, a former Treasury deputy assistant secretary who lobbied against the proposal.

Department of Housing and Urban Development officials said earlier that the administration had relaxed the proposal only for limited partnerships in the low-income housing business. But Treasury officials said yesterday the decision to do away with the limitation entirely had been made some time ago.