Multiple-access interference (MAI) and beat noise (BN) in coherent time-spreading optical code-division multiple access (OCDMA) system are analyzed according to aperiodic cross-correlation function. The mean intensity of aperiodic cross-correlation depends on the transit delay of interfering users, and MAI and BN will change with the mean intensity of aperiodic cross-correlation accordingly. The relationship between the mean intensity of aperiodic cross-correlation and MAI and BN is deduced, and then the relationship between the bit error rate (BER) and the mean intensity of aperiodic cross-correlation is discussed for coherent time-spreading OCDMA. For Gold sequence with the length N=511, mean and upper bound of BER performances are derived according to the different transit delay of the interfering users in coherent time-spreading OCDMA system. In the case of mean BER performance, OCDMA system can support about 12 interfering users. However, for the worst case (upper bound of BER), OCDMA system can support no more than 4 interfering users.