A fast photo-acoustic (PA) imaging system was developed and tested on phantom sample, which consists of an acoustic lens，a multi-element linear transducer array, and the peak detection circuit. The multi-element linear transducer array consists of 64 elements. By utilizing an acoustic lens, the PA signals generated from the sample are imaged and detected by a multi-element linear transducer array, which directly changes the PA signals into the homologous electronic signals. Thus we can map the image more rapidly, with the peak detection circuit, which was designed specially. Compared to other exiting technology and algorithm, the PA imaging system based on an acoustic lens and the peak detection technology was characterized with speediness and real-time. The images reconstructed in this experiment have high definition and resolution，and may have potential for developing an appliance for clinical diagnosis.