A scheme of multi-wavelength OCDMA(MW OCDMA) decoder is proposed,which employs several optical hard-limiters to reduce multi-access interference(MAI).The performances of bit error rate (BER),spectral efficiency and normalized throughput are studied.The results show that BER of MW OCDMA system is improved by the scheme.Increasing the number of simultaneous users under a desired BER,spectral efficiency will also be improved.At the same time,optical hard-limiter can enhance the normalized throughput of MW OCDMA system.Especially the peak of normalized throughput is doubled.