Microwave-induced thermoacoustic imaging (MTAI) is an emerging physical imaging technology that combines the high resolution of ultrasound imaging with the high contrast of microwave imaging and the advantages of deep penetration of microwave. MTAI uses microwave as the excitation source and ultrasound as the information carrier, through the transformation of microwave to ultrasound energy transfer form to achieve non-destructive, high-resolution imaging of biological tissue at a depth of centimetres. The contrast of MTAI image is determined by the difference of microwave absorption. In biological tissues, polar molecules such as water molecules (molecular polarization loss) and ions (ion polarization loss) are mainly used as signal sources to obtain structural and functional images of biological tissues. After more than 20 years of development, MTAI has been applied to imaging various biological tissues and detecting multiple diseases, such as brain imaging, breast imaging, joint imaging, prostate cancer detection, cerebral hemorrhage detection, etc. This paper provides a comprehensive review on: (1) the principle of MTAI, (2) application in the biomedical field, and (3) future development direction.