A report issued by the Greater Washington Research Center found that more than half of Washington area taxpayers would receive a tax decrease under President Reagan's tax reform proposal, but the report raised the prospect of new disparities in tax burdens borne by residents of Virginia, Maryland and the District.

Virtually all taxpayers who do not itemize, and most families with children or only one wage earner who do itemize, would see their taxes go down, according to the report written by Philip M. Dearborn, vice president of the research center.

However, upper-income families with two wage earners and no children would probably pay more taxes because the reduced federal tax rates under the Reagan program would be offset by the loss of the federal deduction for state tax payments.

Such a family earning $75,000 a year and living in the District would pay about $728 more in taxes, the study said, while a similar family living in Montgomery County would pay $418 more and, in Arlington County, $19 more.

For families who do get a tax break, the size of the break would be determined in part by where they live. A family of four with one wage earner who makes $75,000 a year could receive a $1,585 reduction living in Arlington County, but just an $838 break living in the District.

Overall, the study shows, lower-income taxpayers would receive the largest proportional benefits under Reagan's proposal.

A family of four with one wage earner who makes $10,000 would receive a 20 percent tax reduction living in the District, 21 percent in Arlington and 22 percent in Montgomery.

Under the Reagan plan now being considered by the House Ways and Means Committee, differences in tax rates among the three jurisdictions in some cases would be amplified by the elimination of the state tax deduction: The higher the state tax rate, the less the benefit from the tax plan. The study shows this is especially true for higher-income families.

"The increased regional disparity in tax burdens at the higher tax levels will disturb the tax equilibrium that has existed in the Washington area in recent years. As a result, there may be an increased incentive for higher income people to locate outside the District," the report warns.

In an interview, Dearborn said, "The District might have to give some extra relief at the high end of the tax scale because of the magnifications of the disparity."

The consequences of the Reagan proposal for state governments would likely be significant, the study concludes. The closing of tax loopholes to broaden the tax base would produce a windfall to local taxing authorities, with as much as $34 million going to the District, according to the study's estimate.

States would have the option of lowering their income tax rates or using the increased income tax revenues to lower other taxes.