The House Appropriations Committee, rebuffing budget-cutting proposals by the Reagan administration, voted yesterday to allot more than $200 million for Metro subway construction next year, mainly to build a section of the long-delayed Green Line in Prince George's County.

The measure, included in a $10.3 billion spending bill for national transportation programs, was adopted one day after the Reagan administration ended a two-year stalemate over Metro funds and released $391.2 million to expand the subway system.

Despite Wednesday's agreement, the administration had urged Congress to cut off further spending for Metro construction as part of its effort to hold down federal deficits.

Under the new accord, the transit authority plans to complete two major sections of the Green Line in the District and Prince George's County along with a Red Line extension to Wheaton and a Yellow Line spur to Alexandria's West End. The subway extensions are scheduled to open in the early 1990s.

The $217.2 million appropriation endorsed by the House committee yesterday would be earmarked chiefly for an additional Green Line station in the county, at College Park. The allotment represents the same spending level as this year's appropriation for Metro.

Prospects for the measure on the House floor and in the Senate are unclear. However, recent House and Senate budget plans called for $217.2 million for Metro construction in fiscal 1987.

The House committee turned aside proposals by the Reagan administration for other cutbacks in mass transit spending, including operating subsidies. The Metro system receives millions of dollars a year in federal aid to subsidize service and buy buses and equipment.

In other developments yesterday:Metro officials announced plans to construct a $450,000 sound barrier this year at a recently opened rail maintenance yard at West Falls Church to reduce noise in surrounding neighborhoods. Noise at the yard has sparked protests from community residents. The Metro board approved an agreement for a private development project at the Ballston station in Arlington. A Metro spokesman said the accord would provide $8 million in revenue for Metro over the next 10 years.