Photoacoustic imaging, as a new imaging technique with high optical contrast and great ultrasonic detection depth, is a breakthrough of the barriers that the resolution and imaging depth of the traditional optical imaging technique are mutually restricted. It has obtained the unprecedented rapid development. In addition, photoacoustic microscopy inherits the advantages of the photoacoustic imaging technology, and has realized high-contrast and high-resolution biological structure, molecular and functional imaging by using acoustic or optical focusing imaging mode, and it has potential application value in neurology, ophthalmology, vascular biology and dermatology. Here, the principle and classification of photoacoustic imaging technology are firstly presented. Then, focusing on the theme of photoacoustic microscopy, we review its novel scanning methods, focal depth extension techniques and biomedical applications in depth. Finally, the challenges of the development of photoacoustic microscopy are summarized, and the future development direction is also prospected.