Photoacoustic imaging (PAI) is a state of art biomedicine imaging technique in the 21st century, for it inherits the high resolution of ultrasonography in deep tissue and the ability of optical imaging in biochemical information detection simultaneously. The recent progresses of PAI in biomedicine are reviewed. The basic principles and two major implementations of PAI, photoacoustic tomography and photoacoustic microscopy are introduced. Then the capability of multi wavelength PAI in evaluating chemical components in tissues, and the feasibility of PA spectral analyses in evaluating histological microstructures in biological tissue are demonstrated, at the same time, several analysis methods and clinical applications of PAI in biomedical imaging are discussed. Finally, the advantages and potential applications of PAI in biology and medicine are sunmarized.