The microseismic monitoring data have low signal-to-noise ratio and contain lots of noise with different characteristics.The location accuracy of the microseismic event depends on the signal-to-noise ratio of microseismic monitoring data.In microseismic monitoring data processing,it is very important to improve the signal-to-noise ratio.The improved S transform,which has high time-frequency solution,is useful for microseismic monitoring data.Microseismic events can be better processed in time-frequency spectrum than in conventional Fourier transform.Based on the fine focus in time-frequency domain and flexible window function choice of improved S transform,the authors designed a 2D time variable time-frequency filter,which was used to process micro-seismic monitoring data.The combined signal and field micro-seismic monitoring data demonstrate the feasibility and efficiency of the method.