In order to suppress noises in fluid pressure signals, an adaptive filter ing algorithm by using wavelet transform was proposed. The fluid pressure signal and the noise both have different features after wavelet transform on different scales, which lay a foundation for the algorithm. Firstly, the signal was decomposed with wavelet on multim scales, and then av ariety of signal filtering parameters were determined for different scaled signa ls. Finally, an adaptive filter processing was conducted. The filtering result of the pressure signal obtained in the hydraulic system shows the method is more effective than others.