Presented is a distributed optical fiber temperature measurement system for ship cable based on Raman scattering. In order to effectively improve the signal strength, the circuit for detecting and amplifying the weak optic signal was optimized, and the FPGA & DSP was adopted to speed up data processing. Aiming at low SNR (signal to noise ratio) of Raman scattering signal, de-noising method of accumulative average and adaptive wavelet threshold filtering were applied to deal with the measured signals, which not only shortens the measurement time but also improves the SNR. Experiments show that the measuring distance of the designed system ranges up to 4km. The temperature accuracy is 0.1℃, the spatial resolution is 1.5m and the response time is about 3.8s, which presents excellent comprehensive performance and satisfies application demands.