This paper calculates the largest Lyapunov exponent and correction dimension of the fractional order unified system when changing the system parameter, and studies the dynamical behavior of this system. Based on the stability criterion of linear systems, a new approach for constructing projective synchronization of fractional order unified system is proposed. Numerical simulations of fractional order Chen system, fractional order Lü system and fractional order Lorenz-like system are provided to demonstrate the effectiveness of the proposed scheme.