Code division multiple access (CDMA) can be adopted to make full use of the broad bandwidth and effectively improve the system performance of wireless optical communication system. Considering the effects of background optical noise, multi-user interference, avalanche photodiode detector (APD) noise, and atmospheric scintillation, the system model of atmospheric two-dimensional wireless optical code division multiple access (2D-WOCDMA) communication system with pulse position modulation (PPM) and fiber Bragg grating (FBG) encoder/decoder is presented. And the bit error rate (BER) of this optical CDMA communication system is analyzed in detail. The results show that atmospheric scintillation is one of the important factors which affect the BER performance of this communication system, and the 1550 nm wave band is more suitable for this 2D-WOCDMA communication system. When the atmospheric turbulence is strong (σ2s≥0.2), some new technologies,such as multi-user detection, channel coding and array reception,can be used to improve the system performance. The results also show that the performance of this communication system can be affected by background optical, APD gain and modulation extinction ratio.