The D.C. Historic Preservation Review Board called for changes yesterday in a multimillion-dollar plan for renovating Union Station after officials warned that some proposed commercial development would "obscure the architectural character" of the historic structure.

The advisory panel was the first of several local and federal agencies expected to review the plans for the building, which was closed in 1981 because of leaks in its roof and other deterioration.

The architectural plans, drawn up largely by Benjamin Thompson & Associates Inc. of Cambridge, Mass., would require extensive changes in the interior, but preserve the exterior. The redevelopment is expected to be completed by mid-1987 at a cost of nearly $140 million in federal and private funds.

The preservation board urged that the "development concept be restudied" in an attempt to resolve issues raised by city preservation officials and board members.

Harrison M. Ethridge, a college administrator and history professor who serves on the board, argued that plans for the building's main hall showed "too informal an approach." Colden Florance, an architect and board member, urged developers to "avoid trivializing" the building with inappropriate commercial outlets.

Tanya Beauchamp, an architectural specialist in the city's Historic Preservation Division, recommended revisions in the plans, including eliminating a proposed mezzanine extension in one hall and what she termed a "proliferation of trees, kiosks and other structural elements."

The plans "do not take full advantage of the unique architectural character of Union Station, but seek to modify this character to accommodate a previously successful theory of commercial design," she said.