Spread spectrum communication is known as a great breakthrough in communications technology. The RF bandwidth used to transmit information is much wider than the information itself. Spread spectrum communication improves the anti-interference ability greatly, reduces power consumption and has become the key technology in modern communication. This paper presents a FPGA-based simulation for digital communication model in QUARTUS 9.0 environment, lays emphasis on designing and implementing the modulator of spread spectrum communication system and verifies the correctness of the modulator by simulation. The modulator is of universality and easy to realize, greatly reducing the development process.