Abstract: In this research, in order to eliminate the adverse effect of rainfall weather on the detection results of evaporator water surface evaporation, a mobile phone on-line control device for evaporator based on automatic rainproof and early warning push function was designed. The device consists of 57BYG250B stepper motor, coupler, limit switch, bearing, touch rod, rotating arm, 20 rain sensors and rain cover. The rotating arm and the touch rod were fixed on the supporting rod, and a bearing was fixed below the touch rod to ensure that the supporting rod would not flutter when it rotated. The clockwise and counterclockwise rotation of the supporting rod were driven by 57BYG250B stepper motor. The drive shaft of the supporting rod passing through the bearing and the 57BYG250B stepper motor were connected and fixed by the coupler. The limit switch was installed in the same plane position and parallel to the touch rod. A rotating arm was fixed on the supporting rod, and the rain cover was installed on the rotating arm. The output shaft of 57BYG250B stepper motor was connected with the supporting rod through the coupler. 20 rain sensors were connected in parallel to automatically detect whether there is rainfall by judging if the rain sensors output low level. The rotation of 57BYG250B stepper motor drove the rain cover to completely shield the evaporator and returned to its initial position. The data transmission format between Internet of Things server and push server, Internet of Things server and mobile app, Internet of Things server and the device developed is JSON. The Internet of Things server was called public API of weather forecast regularly, and the mobile terminal integrated GeTui SDK for rainfall warning, evaporator completely-shielded and backed to initial position. The MCU program uses C language to compile the code of rainproof and removal of rain cover, and encapsulates it. The mobile program sent rainproof instructions or the rain sensor detected rainwater falling on the surface of the sensor, which would call the rainproof function. When the mobile program issued a rain-shield removal instruction or the rain sensor was dried, the rain-cover removal function was produced. The mobile program called the instruction sending function in Objective-C language and passed the corresponding instruction parameters. The stability and reliability of the device were verified by testing the performance of 20 rain sensors and 57BYG250B stepper motor. The results showed that 1) the device was reliable in operation. In 60 tests, the success rate of complete shelter and returning to the initial position of the rain shield was 98.3%; 2) the operation of the device was stable, and the error range of the theoretical angle of the support rod rotation and the measured angle was 1.6°-3.5°, the maximum relative error was 4.1%, and the minimum relative error was 1.9%; 3) In the reliable test of 60 message pushes, the success rate of receiving feedback messages was 98.3% after the rain and the rain cover were removed successfully. Field test results showed that 5 days in 14 days are rainy days. The rain warning message has been received before it rains. The device has strong adaptability and good performance and its maximum error range was 3.4°. The device could not only automatically passes perception of rainfall to rainproof, but also be operated online by mobile phone to give early warning notice for rainy weather. The successful push message of the evaporator completely blocked by the rain cover and returned to the initial position, which improved the intelligent level of the evaporator rainproof operation. This research provided new ideas for the application of intelligent rainproof technology and message push technology in the development of agricultural intelligent equipment.