A rebellious Senate defied veto threats and passed a farm bill yesterday costing billions more each year for corn and wheat price supports than President Carter has called acceptable. The vote was 69 to 18.

Senate Budget Committee Chairman Edmund S, Muskie (D-Maine), lost in two attempts to slash the price support levels in the bill back to what Carter wants, 50 to 45 and 51 to 43.

Former GOP vice presidential candidate Bob Dole (R-Kan.), opposing Muskie, said, "The administration is up here trying to help the farmer."

Dole said that before the election Carter was promising to help the farmer and criticizing President Ford's veto of a similar bill, but "now the Secretary of Agriculture almost daily is threatening veto."

Muskie, who said he offered his amendments to prevent the farm program from breaking the budget in fiscal 1978 and future years, said in a tone of irony after the votes, "The Senate voted to support the President's campaign promise."

Farm-bloc Democrats like Hubert H. Humphrey (D-Minn.), George McGovern (D.S.D.), Quentin N. Burdick (D.N.D.)and Lee Metcalf (D.Mont.) opposed Muskie.

The Senate bill sets price supports for wheat at $2.90 a bushel for 1977 and $3.10 for 1978, with the guarantees thereafter to be increased in accord with boosts in the cost of production. Carter, even after revising initial proposals upward, had asked for only $2.47 in 1977 and $2.90 in 1978.

The bill sets supports for corn at $2.28 a bushel in 1978 with subsequent boosts based on production cost rises. Other feed grains would be based on corn support levels.

The House Agriculture Committee has approved figures closer to Carter's - $2.65 in 1977 and $3 in 1978 for wheat, and $2.10 for corn. Administration spokesmen are hoping these figures are retained or lowered on the House floor and then inserted in conference in place of the higher Senate figures - in which case a veto would probably be avoided.

Administration spokesmen said the figures set by the Senate could cost up to $2 billion a year more than under Carter's proposals, making it impossible to realize Carter's goal of a balanced budget by 1981.

In addition to setting prices for wheat and corn, the bill also sets price systems for milk, wool, cotton, rice, peanuts and soybeans, but three-quarters of the estimated $4 billion average annual cost of the crop programs from 1978 to 1982 result from the wheat and corn provisions.

The bill also sets up a system of grain reserves and authority for special overseas sales and donations of foods. It authorizes continuation of the food-stamp program, at about a $5.5 billion cost a year, with 17 million to 20 million recipients, until Sept. 30, 1979.

The bill makes major changes in the food-stamp program, the most important to eliminate the requirement that an eligible family purchase the stamps.

Under existing law, an eligible family entitled to stamps would, for example, pay $100 to the government to purchase stamps worth $160 when used at the grocery store to buy foods. The $60 difference is called the "stamp bonus" and is ultimately paid for by the government. Under the Senate bill, the family would pay nothing and would simply get $60 worth of stamps.

Carl Curtis (R-Neb.) warned that by eliminating the purchase requirement, the bill made it too easy to get stamps, and predicted many more eligible persons would seek them. About 35 million are eligible but only half that number actually participate in the stamp system. His amendment to restore the purchase requirement failed, 64 to 31.

A move by McGovern to extend the program for five years instead of two was beaten to 49 to 46 after senators said a five-year extension would fore-close integration of the stamp program into a new overall welfare system Carter wants to install in a few years.

The Senate bill also reduces participation of middle-income families in the food-stamp program by eliminating some of the deductions from income which an individual may make in determining whether his income is low enough for stamp eligibility. The only deductions from gross income allowed would be $60 a month as a general deduction, $85 a month for care of a dependent while you are working, 20 per cent of earnings for work expenses, and up to $75 a month if the applicant has extra-high rent.

A family would be eligible for stamps if after these deductions its remaining income were no higher than the poverty line $5,850 at presrent for a family of four, $4,890 for a family of three). The Congressional Budget Office estimated that the removal of the stamp-purchase requirement would encourage about $1.2 million persons to seek benefits who don't apply nos, but that the tougher eligibility requirements would eliminate an equal number of recipients.