The Supreme Court yesterday agreed to decide whether Iowa's method of taxing corporations is constitutional.

The method has drawn heavy fire from corporations, economists and other critics who say it is discriminatory, irrational and a "protectionist" burden on interstate commerce.

Iowa taxes corporations solely on the basis of the share of net income "reasonably attributable to" the trade or business they do within the state's boundaries.

Other states use a formula that relates payroll, property and sales within their boundaries to the same three factors on a national scale.

Under the Iowa formula, the Moorman Manufacturing Co. of Quincy, Ill., an agricultural supplier with a largr operation in Iowa, was billed for 22.6177 per cent of its 1968 net income of $97.7 million. Under the three-factor formula, it would have been billed for only 14.1088 per cent, the firm said.

The Iowa plan "blatantly discriminates" against manufacturers chartered outside the state, Moorman protested. It charged that the Iowa formula bears no relation either to a firm's activities within the state or to the benefits it received there.

Similarly, the Motor Vehicle Manufacturers Association of the United States, a trade group for the domestic auto industry, says that in 1976 alone, Iowa billed its members for $3.7 million more than they would have been assessed under the three-factor formula.

The Moorman firm argued in state court in Iowa that the state's formula violates the U.S. Constitution by denying due process of law and the equal protection of the laws, and by burdening commerce among the states.

Last May, the Iowa Supreme Court rejected Moorman's charges, mainly on the ground that the state was empowered to adopt and enforce a one-factor formula.

The auto industry, in an amicus curiat of friend-of-the-court brief, told the U.S. Supreme Court that the Iowa law has "created a protectionist wall favoring local corporations and giving them a competitive advantage" over rivals based elsewhere.

In another amicus brief, the Committee on State Taxation of the Council of State Chambers and Commerce said the Iowa court decision encourages "an emerging trend toward parochial and protectionist state taxation of interstate commerce."

Similarly, 17 economists, including Nobel Prize Winner Milton Friedman, warned that the Iowa decision, if allowed to stand, will raise the "specter of a severely damaging, yet not openly declared trade war between the states."

The economists, who compared the Iowa formula to a tariff, said their concern was with its anti-competitive effects and potential. They provided data to show that Iowa corporations fare much better in other states than out of the state firms fare in Iowa.

Lawyers for the Moorman company said more than 50 firms fare in Iowa.

Lawyers for the Moorman company said more than 50 firms doing business in Iowa have filed legal challenges to the single-factor formula.

In other Supreme Court actions:

Savings and Loan Taxation

The court has agreed to hear an appeal by federal savings and loan associations in Massachusetts from a decision in which the state Supreme Judicial Court upheld a state tax law barring inclusion of payments of interests and dividends to shareholders among operating expenses. The associations claim - and the state denies - that the law gives an unfair advantage to rivals. Alaska Pipeline

Last June 28, the Interstate Commerce Commission began an investigation into the lawfulness of the rates proposed by the owners of Trans-Alaska Pipeline System for shipping oil: $6.04 to $6.44 a barrel. Meanwhile, the ICC said, it would accept interim rates of $4.68 to $5.10.

The principal owners - pipeline subsidiaries of Mobil, Exxon, British Petroleum and ARCO - challenged the agency. As a result, the Supreme Court on Oct. 20 stayed the ICC-ordered interim rates pending review of the case on the merits.

Yesterday, the court, in a 4 to 3 action, ordered the owners to keep account of the sums they collect, in even the justices ultimately order a refund.

In a dissenting opinion, Justice William J. Brennan Jr., joined by Justice Thurgood Marshall, said he had approved the star, but now feels that it was "improvidently and precipitately issued and that it should be dissolved." Justice Harry A. Blackmun dissented separately.

Justice Potter Stewart and Lewis F. Powell Jr. did not participate.