The performance of optical code-division multiple-access (OCDMA) system with an encoder/decoder based on step chirped fiber bragg gratings (SCFBGs) is presented. In the system, the multiple access interference (MAI) is the main noise and the unsuccessfully decoded pulse is assumed to be a Gaussian random process. Simulation shows that longer code length and narrow pulse improve the performance of system. And when threshold is 0. 7, the best bit error rate (BER) can be obtained for this OCDMA system.