Abstract: The OCDMA system is briefly introduced. The code pattern and code capacity, the role of sequence spread spectrum to the security of OCDMA are analyzed, the expectations of the frequency of the correct address code detection is given with complete error-free detection probability and the address code detection to the security of OCDMA is analyzed. The relationship between OCDMA technology and modern fiber-optic secure communication technology is compared. Some measures to increase security of the OCDMA system are put forward.