The influence on system characteristics of fiber optical gyroscope(FOG) of phase drift of modulator when Y-waveguide phase modulator used in FOG reset were analyzed. Afterward ,the millisecond output of high-precision FOG was tested, one kind of nosie which was synchronization to stepwave reset was caused by Y-waveguide reset .In order to suppress reset noise,one kind of wavelet filter is designed based on FPGA. Appropriate wavelet basis function and layers of wavelet packet was selected. Wavelet filter was nested in the program of closed-loop control FOG by the program language of Verilog HDL. The comparison of experiments show that the effect of reset noise suppressed is more availability, it is proved that the design of wavelet filter is valid.