Treasury Secretary Donald T. Regan said his department is preparing a revised corporate minimum tax and will propose legislation to prevent companies from using excess write-offs on new investments to cut taxes on other income, giving themselves what amounts to a federal tax subsidy.

"We are going to change our concept," Regan said yesterday, acknowledging the massive Congressional opposition to the administration's original corporate minimum tax.

A House-Senate conference committee has agreed to a fiscal 1983 budget requiring about $21 billion in new taxes. At a luncheon interview at The Washington Post, the Treasury secretary said he would prefer to reach this goal through enactment of many small tax increases "because you get into the large ones and you have to make major changes in the tax structure." He did not rule out possible administration support of a broad energy tax, however.

Regan said no proposals have yet been cleared by President Reagan, and he refused to detail the form of the new minimum tax. One proposal under consideration by the Treasury, however, is an across-the-board reduction of 15 percent in all tax preferences.

Tax preferences include such breaks as percentage depletion, accelerated depreciation on real property, intangible drilling costs, tax deferrals from creation of a domestic international sales corporation and deductions for debt to carry tax-exempt securities.

In addition, the Treasury secretary said he intends to press for legislation that would eliminate from current law negative tax rates on the profits from new corporate investments.

For certain kinds of investments, including construction machinery, general industrial equipment and trucks, the 1981 tax bill gave such generous breaks that, not only are the profits from these acquisitions effectively tax-free, but excess credits and deductions also can be used to reduce a company's taxes from other sources of income, such as an older factory or an oil well.

The tax system "will not go into negative rates," he said. "Now as the head of a corporation, you may say, 'The hell, if I can get my taxes down to zero, why not.' But if you ask the average person whether corporations should pay taxes, the answer is 'yes, a corporation should pay taxes, regardless of what they do legitimately to reduce taxes, whether it's timber, oil depletion, or investment tax credits or whatever'."

Regan said negative tax rates on new investments could be eliminated without tinkering with the highly accelerated depreciation schedule enacted last year. He did not specify how this could be achieved, but the Joint Committee on Taxation has included two that achieve the goal in a laundry list of potential new taxes:

* At present, companies get a 10 percent investment tax credit on most new investments, and are allowed to depreciate 100 percent of the cost although the credit effectively functioned to pay 10 percent of the cost of the acquisition. According to the Joint Committee, limiting depreciation to 95 percent of the value of the asset would eliminate the negative rates.

* Similarly, a straight reduction in the investment tax credit from 10 percent to 7 or 8 percent would prevent the tax rates on new investments from falling into negative numbers.

In addition, Regan's position would appear to require repeal of additional accelerations of the depreciation scheduled to go into effect in 1985 and 1986. Repeal would not save any money in 1983 or 1984, but savings would amount to $1.5 billion in 1985, to $9.6 billion in 1986 and to $17.4 billion in 1987.