Washington - based bureaucrats could wind up making more, for doing the same job, than their Baltimore colleagues. But they could get less than the feds in Detroit, Los Angeles and Seattle under President Carter's compensation reform plan.

The key to the salary shakeup the president has sent Congress is a linkage between federal salaries and going rates for the same jobs in local industry.

Nobody has spelled out exactly how the system would work, except in very general terms. The proposal includes weighing the value of government pay and fringes against industry to get a national rate - pegged at 100 - for government.

After that national rate was set, agencies would - perhaps every three years - establish a linkage with their local private industry pay line. The Labor Department already has such comparisons, called "pay relatives," which rank salaries by major cities.

Under that system, Washington ranks at 103 against a national wage average in industry of 100. Detroit is highest with 118; Seattle is 109, Chicago 105. Atlanta is the same as Washington, 103. Baltimore comes in at 100.

Pay relatives for other cities, which will serve as a guide for any area wage plan in government, look like this:

New Orleans, 90 . . . Minneapolis, 95 . . . New York, 106 . . . Norfolk, 85 . . . Sacramento, 106 . . . San Francisco, 111 . . . Boston, 97 . . . St. Louis, 99 . . . Denver, 99 . . . Dallas, 94 . . . Philadelphia, 98 . . . Richmond, 91 and San Antonio, 83.

Los Angeles is 107, San Diego 96 and Miami 98.

Federal officials say the data shows that there is not necessarily a correlation between high costs and wages. Boston, for example, is considered a high-cost city, yet it ranks below Washington, Philadelphia, Baltimore and other cities.

The plan has a long way to go through Congress. The proposition of linking federal wages to local going rates in industry sounds simple enough.But it could be hard to sell employes - and private sector unions - in cities where high costs would not necessarily guarantee top wage adjustments.