D.C. budget director Gladys W. Mack, a key member of Mayor Marion Barry's team for the last four years, is expected to be reassigned as part of a major reorganization the mayor will unveil today.

Barry spent part of yesterday putting the finishing touches on his reorganization scheme, which calls for extensive reshuffling of key personnel and a new table of organization giving the mayor's office more control and downgrading the role of the city administrator.

A new chief of staff and three new deputy mayors, with direct line responsibility for finance and revenue, government operations and economic development, are expected to be appointed by Barry.

Mack, Department of Transportation Director Thomas M. Downs, and mayoral special assistant Courtland V. Cox are thought to be in line for major appointments..

City Administrator Elijah B. Rogers, who directs the day-to-day operation of the city government, is expected to leave his post next year to work in the private sector.

Barry also plans to reorganize several departments and create a new department of licensing and regulation that will be headed by Carol Thompson, current acting director of the Department of Licenses, Investigations and Inspections.

Following his election in November, Barry asked the city's 52 top officials to submit their resignations. More than a third will be reassigned or will leave government.

William H. Rumsey, director of the Department of Recreation and a holdover from Mayor Walter E. Washington's administration, is expected to be reassigned. Several high-ranking officials already have departed or announced they are leaving, including Carolyn L. Smith, former director of the Department of Finance and Revenue; Robert L. Moore, former director of the Department of Housing and Community Development, and James O. Gibson, deputy administrator for planning and development.

Many of Barry's special assistants are expected to leave city government or take new assignments outside the mayor's office, including Kay C. McGrath, Patricia E. Miner, Lillian A. Sedgwick, Warren Graves and Mary Lampson.