The paper reviews the development and results of seismic precursory waves since the 1960s． The significant progress has been made in the development of earthquake prediction research using precursory waves． But there are still some fundamental problems which need working out． The authors discuss the seismic precursory waves from such respects as its definition， basis for the strong earthquake prediction， observation technology， predicting significance，etc． Definition of seismic precursory waves is explained． The characteristics of seismic precursory waves change with time according to some seismic examples，which is also proved from both the theory of isotropic elastic wave equations and the practice of precursor observation． It is reasonable and scientific that the strong earthquake prediction can use precursory waves． The paper elaborates on the development of precursory wave observation technology． In order to actively gain abnormal source signal，the authors suggest that the present observations should be changed to better enhanced monitoring of the focal region． Since seismic precursory waves carry lots of information about medium parameters variations in the focus and its nearby area，it is significant to apply precursory waves to the short-term earthquake prediction．