A new communication technique of transmitting Mary digital signals using projective synchronization based on stability criterion is proposed in this paper. At the sender, Mary digital signals are modulated into Jacobian matrix and the scaling factor of chaotic system. The digital signals are decoded in the corresponding subsystem constructed at the receiver end. Lorenz attractor is taken as an example to simulate the process of transmitting decimal digital signals by chaotic modulation. Numerical analysis shows that the communication system has higher transmission rate and decoding accuracy for the digital symbols without increasing complexity. The security and effectiveness of the proposed technical scheme is validated through the numerical investigation.