The water droplets impact of irrigation equipment is an important technical indicator for measuring nozzle performance. The impact force of water droplets hit the surface of the soil would erode the soil, causing soil compaction, resulting in runoff affect the infiltration effect, while water droplets impact would cause foliar damage, which affects crop growth. This paper developed a droplet impact automatic detection system to measure the water droplets impact force. The PVDF piezoelectric sensor was chosen as the sensing element, and the water droplets automatically generating device was designed by a stepping motor drive and system was controlled by a microcontroller. The USB7333 high speed data acquisition card was used and the program was written in LabWindows/CVI based computer data acquisition and process procedures to detect the water impact force. As the result, in the frequency of water droplets, the size of the stability control experimental conditions, the detection system could achieve the dynamic measurement of different droplets size to show that the PVDF piezoelectric sensor for detecting water droplet impact with good dynamic response. The result proved that the water droplets micro force sensor output voltage had a good linear relationship, and the trend line with the actual data fitting degree of 0.936, the system measurement error less than 10%. This droplet impact force detection system solves the traditional manual measurement method of water droplets instability problems and has great practical application value.