The observation data of 4-component borehole strainmeter at Gaotai base seismic station, Gansu province, have been stable, continuous and reliable since it was set up in 2007. It is found that different types of the precursory waves appeared before some strong earthquakes, such as sudden rise, sudden plunge, tidal distortion and microtremor bold, etc. In this paper the precursory waves before some strong events are introduced, and the mechanism of the wave is discussed also.