Abstract: Aiming at problem of plastic greenhouse temperature and humidity adjustment needs manual operation, which is time-consuming and laborious, a set of plastic greenhouse temperature and humidity system based on PID control was designed．System consisted of temperature and humidity measurement module, control output module, display and alarm module, connectivity and anti-interference communication between each module was strengthened, and efficiency and stability were improved．Algorithm was analyzed and designed, single-factor experiment and comprehensive experiment were carried out．Results showed that when setting preset temperature and humidity initial range at 25 to 27 °C and 50% to 60%, system control average error rate was 1.2%, which met plant growth requirements of experimental crops and provided a reference proposal for automation technology upgrading in plastic tunnels．