The ($alpha$,$eta$)-metric is a Finsler metric which is constructed from a Riemannian metric $alpha$ and a differential 1-from $eta$;it has been sometimes treated in theoretical physics. The condition for a Finsler space with an ($alpha$,$eta$)-metric L($alpha$,$eta$) to be projectively flat was given by Matsumoto [11]. The present paper is devoted to studying the condition for a Finsler space with L=$alpha$ulcorner$eta$ulcorner or L=$alpha$+$eta$ulcorner/$alpha$ to be projectively flat on the basis of Matsumoto`s results.