Abstract: Aiming at problems of inaccurate fertilizer mixing and detection, no specific target for potato crops, and low level of intelligence of current field potato water fertilizer integrated irrigation system in China, a precision control water fertilizer integrated system based on PLC and Internet of Things control was designed and developed． Due to poor growth environment and many unstable factors of potato in the field, the system used PLC control． Compared with control mode of single chip microcomputer, PLC has many advantages such as high reliability, strong anti-interference ability, simple and convenient programming, strong adaptability to harsh industrial environment and convenient construction． Because traditional field water fertilizer machine used a booster pump to directly inject fertilizer absorbed by the Venturi fertilizer aspirator into main pipe to flush natural fertilizer with water, accuracy of fertilizer mixing cannot be guaranteed, and the EC and pH sensors cannot be accurately measured, resulting in inconsistent fertilizer concentrations of crops in the field, and relatively low crop quality and yield． Compared with traditional water fertilizer machine, adding fertilizer mixing chamber could significantly reduce concentration error of water and fertilizer． EC and pH sensors read current water and fertilizer concentration and pH in real time, perform PID calculation with preset value, and then converted the PID output into pulse output time through linear conversion． The on-off fertilizer suction time of Venturi solenoid valve was controlled through PLC output to achieve accurate adjustment of water and fertilizer concentration, and water pressure fluctuated within set value range with constant voltage frequency conversion cabinet to achieve accurate and stable output of water and fertilizer．