Encryption is vital for protection of data and intelligence property, which is often used to encrypt products by software.However, software encryption has some shortcoming such as mass operations and easy being simulated. Hardware encryption has high security because this method can relieve burden of MPU and has physical protection layer.We can use high randomicity of chaotic algorithm as generator for cipherkey in order to combining software and hardware to realize respective value.Through VHSIC hardwaredescription language to design FPGA, cryptography can use hardware to realize chaotic algorithm and software to manage hardware by sending control signal.The experiment has proved that this method can enhance operating efficiency of algorithm and strengthen security of cryptography.