Abstract: The research and development of a transmission scanning acoustic microscope operating at 300-700MHz is described. The design and construction of the microscope, the acoustic transducer-focusing system, the mechanical microwave and electronic systems are presented. Theoretical analysis and experimental results show that the resolution of the microscope is not worse than 2μm, i. e. the resolution reaches the refraction limitation. Finally, images of some specimens obtained by using the acoustic microscope are given.