Ultrasonic signal can cause the SU-8 material thickness change. Based on this, a uniform thin layer thickness of the SU-8 film is plated on the cover glass, the smooth reflecting surface is coated with a layer of uniform metal silver, and then a photoacoustic sensors is made. And a set of real-time, dynamic photoacoustic imaging system is proposed based on the sensor. In this system, the photoacoustic signal of absorbent sample causes the SU-8 material thickness change on the photoacoustic detector. When the laser through the reflector of detector, the changes of thickness will modulate the phase of reflected light. The phase shift is demodulated using the optical phase contrast filter method, and the thickness variation of SU-8 is obtained. The corresponding light distribution of photoacoustic signal of samples is acquired, and the dynamic real time photoacoustic images are obtained. The generating (ultrasonic effect), modulation and demodulation (production of the sensor) of photoacoustic signals are discussed. The response characteristics of photoacoustic signals are studied experimentally by SU-8 photoacoustic detector, and the results indicate that SU-8 can detect photoacoustic signals.