In order to analyze and study the influence of laser focusing position on photoasound signal of gold nanoparticles, ultrasound detectors were used to detect ultrasound and the state of solution was observed by CCD. The results show that, when the laser pulse is focused in the middle of the colorimeter, the photoacoustic signal is the ultrasonic signal of gold nanoparticles suspended in solution under the action of laser. When the laser is focused on the interface between the inner wall of the colorimetric dish and the solution, the photoacoustic signal duration of gold nanoparticles increases and becomes disordered. In this case, if the ultrasonic signal oscillates periodically, the solution of gold nanoparticles starts from the laser focus and flows at high speed along the laser direction. This research has certain reference significance for opening up a new research field of microfluidics.