A multi-channel all-optical modulation format converter from non-return-to-zero (NRZ) to return-to-zero (RZ) is reported based on the fiber optical parametric amplifier (FOPA). In this scheme,the NRZ data together with a synchronized pump clock are injected into the highly non-linear fiber (HNLF). The FOPA consisting of HNLF converts the NRZ signal to RZ signal,and the wavelength of the signal is preserved. The multi-channel operation at 10 Gb/s is demonstrated experimentally. The sigal to noise ratio (SNR) of the converted RZ signals is no less than 7.6 dB with 3 dB enhancement of extinction ratio (ER). The pulse-width of the obtained RZ signal is around 30 ps. According to the operating principle of the multi-channel code converter,the converter is considered to be proper for the multi-channel operation at 40 Gb/s or even higher bit-rates.