The invention discloses an underwater distributive PTV flow field measurement system and a measurement method thereof. The system comprises a river model, tracer particles, a set of smart cameras, a set of POE switches, a wireless router and a flow field computing system. The tracer particles are evenly distributed in water flows of the river model, the smart cameras are installed above the surfaces of the water flows of the river model, the smart cameras are connected with the POE switches, the POE switches are connected with the wireless router, the wireless router is communicated with a wireless local area network card, and the flow filed computing system is connected with the wireless local area network card. The invention further provides an underwater distributive PTV flow field speed measurement method based on wireless measurement. According to the method, an algorithm is embedded in the smart cameras for processing, the measurement speed is improved, measurement data can be directly output, and the technical problems that in the prior art, the quantity of output image data is large, wireless measurement cannot be achieved, and instantaneous measurement cannot be achieved due to low processing speed are solved.