A method of projective synchronization based on stability criterion of linear systems is introduced and a technical scheme of chaotic masking for secure communication is proposed. A nonlinear drive vector function of special chaotic state variable is constructed with scaling factor α for chaotic synchronization by separating linear and nonlinear terms properly. Transmission information is injected into one element of state vector as carrier signal. Complexity of masking information and decoding difficulty is increased. Lorenz attractor and hyper-chaotic Rössler attractor are used as an example to simulate sinusoidal information. Amplitude and frequency of signal can be chosen in a wide range. Added scale factor α makes decryption process more complex, thus improving security of communication. The method is proved effective for secure communication.