Employing microcavity coupling technology, a microcavity photoacoustic transducer with high sensitivity is proposed. The transducer works like this: the photoacoustic (PA) waves, which carry the information of the sample, transmit across the microchannel to the coupling cavity and are detected by the microphone. In the same case of the temperature change, the pressure variation in an airtight cavity is inversely proportional to the volume of the cavity. So the sensitivity of transducer can be effectively increased by using the microcavity structure, which is more sensitive to the feeble PA signal induced by a modulated continuous wave laser source. By using the technology, the photoacoustic microscopy (PAM) images of onion epidermal cells and RBCs are clearly reconstructed in cellular resolution. The result of resolution test target verifies the resolution of the PAM with microcavity PA transducer is better than 1.25 μm.