The partially projective synchronization of a class of chaotic systems was investigated.We presented a stability criterion for the partially projective synchronization in three-dimensional systems,which was proved theoretically via Lyapunov method.This criterion can be used not only in three-dimensional chaotic systems but also in four-dimensional hyper-chaotic systems for two-variables partially projective synchronization.Finally,some numerical simulations with the chaotic Lorenz system and the hyperchaotic Lü system were given to demonstrate the correctness and effectiveness of the stability criterion.