The scheme of 1 Gbit/s random sequence generated by chaotic laser as spreading code is proposed. Theoretical analysis indicates that the pseudo random sequence exhibited periodic behavior is eliminated by the random sequence and the capability of spreading code is enlarged. Meanwhile, the communication security can be improved by variable spreading code. The corresponding spread spectrum system is numerically simulated by Simulink software and the results demonstrate that the greater the used spreading gain, the lower the obtained error rate will be when the information speed is constant, which is consistent with the theoretical results. The anti-jamming ability of the spread spectrum system is strengthened and the security is enhanced compared with those of the traditional spreading system.