Academician Wang Chenghao established the generalized green function theory for surface excitation of piezoelectric crystal, which laid theoretic foundation for modern acoustic surface wave technology. According to this theory, he analyzed the diffraction field generated by surface excitation of piezoelectric crystal, which overcame the disadvantage of the popular angular spectrum theory and got the accurate expression of the diffraction field of acoustic surface wave in surface grating array. He developed a series of devices and systems for acoustic surface wave and high-frequency wave. Based on the research of the electric load characteristics of piezoelectric vibrational system, he brought forward the structure of piezoelectric adaptive tuned transducer and the damping theory of piezoelectric vibration. He also carried out a series of researches on single cavitation bubblesonoluminescence. It was he who discovered that there was also electromagnetic radiation besides the ray radiation and proved that all the radiation happened in the cavitated closure instant.