The paper analyses the effects of intra-channel four-wave mixing (IFWM) on the high-speed optical fiber communication system. A new code format is developed with double 0 and double p phase separating 1 code; it can decrease the transmission penalty from fiber nonlinearity by counteracting the perturbation terms of IFWM. From the simulation of transmission of two classic code data ‘‘11011’’ and ‘‘11100’’, we find that our proposed code format has a better suppression effect than the alternative modulation inversion (AMI) or the normal RZ format and supports a wider pulse mode. In a 40 Gbps system, the AMI format is 2 dB less than the RZ format, and our proposed format is 1 dB less than the AMI format when a 1 dB eye open penalty is taken as a metewand. Moreover, it can be realized as easily as the AMI format.