Two new buildings for the Mall -- one housing temporary exhibits of Oriental art, the other a new home for the Museum of African Art -- are being considered by the Smithsonian Institution.

A $130,000 study due April 15 will examine the feasibility of low, one-or two-story buildings. They would parallel Independence Avenue, across the Victorian garden from the Castle. They would be east of the Freer Gallery and west of the Arts and Industries building, making a quadrangle court of the garden.

Japanese architect Junzo Yoshimura is making the preliminary design study. The study is funded by private Smithsonian monies, appropriated by the Board of Regents. A spokesman said the estimated $55 million to build the new museums probably would have to come from Congress, with the help of some private donations.

The galleries for showing Oriental objects would permit the Freer to have temporary exhibits for the first time. By terms of the Freer bequest, the gallery can only show works from its own collection. The new building would have only an underground connection with the Freer.

The new building proposed for the African Art Museum would also hold the Smithsonian's rare book collections as well as some other archival material.

The Independence Avenue entrance to the quadrangle might be used to hold a pair of ornate gates, designed for the Castle by its original architect, James Renwick, but never executed.