The invention discloses a downhole microseismic three-component rotating method and belongs to the field of downhole microseismic three-component signal processing. The method includes: firstly, inputting an X-component and a Y-component, then solving extreme values to obtain an X-direction azimuth and a new R-component and a new T-component; secondly, inputting a Z-component and the R-component prior to solving extreme values to obtain a Z-direction azimuth and a new P-component and a new S-component; finally, taking the P-component, the S-component and the T-component as rotating results of the original X-component, Y-component and Z-component. By the method, accurate rotation of the downhole microseismic X-component, Y-component and Z-component can be realized, the new three components P, S and T uniform in amplitude are obtained, and information such as wave propagation and the azimuth theta of the X-component and the azimuth phi of the Z-component can be obtained. In addition, the method is small in influence of noise and stable in computed results, and input data are unlimited to P-waves or S-waves.