Abstract: Abstract: The technology of plastic greenhouses is widely used in China. Greenhouses’ films get dirty easily with dusts and mosses with the increasing of use time. That’s the reason why its transmittance (which is one of the important factors that affect the greenhouses’ productivity) decreases. Nowadays, cleaning devices are mainly designed for glass curtain walls, ventilating ducts and air conditioner pipes. These cleaning devices have difficulties in cleaning plastic greenhouses because of the greenhouses’ arc frames and the films’ variable surfaces. To solve the problems, a cleaning device with magnetic wheels was designed in this paper. The cleaning device consists of magnetic wheel walking mechanism and brush cleaning mechanism, whose core components are magnetic wheels, walking motors, brushes and cleaning motors. When greenhouses need cleaning, put the device on the greenhouses’ canopy and provide power for it. Thus, the walking motors can drive the magnetic wheels to walk forward on the greenhouses’ frame by magnetic absorption. Meanwhile, the cleaning motors also drive the brushes to clean the greenhouses with water or detergent for the first time. When the device walks to the top of the canopy, manually shift the power switch to make walking motors rotate reversely, then, the device can walk back and operate the second cleaning work. When the device returns to the bottom of the greenhouses’ frame, it should be translated to the neighboring frame for the next cleaning work. The device’s minimum driving force and magnetic force were calculated by the device’s mechanical model and its force situation analysis, which was essential for walking on the greenhouses’ frames. The analysis results showed that the driving force and magnetic force needed at least 58.9 and 235.6 N, respectively. And each magnetic wheel’s magnetic force was no less than 58.9 N. In order to verify whether the magnetic wheel met the requirements of minimum magnetic force, the magnetic force analysis was taken in ANSYS and the analysis results indicated that each magnetic wheel’ magnetic force was 67 N, which had met the requirements. In order to balance the cleaning effect and working efficiency, the device’s theoretical walking speed was computed and designed to 0.13 m/s. Based on the design and calculation of the magnetic force, driving force and walking speed, the cleaning device can walk safely and stably on the arc frame of plastic greenhouses with skeleton spacing of 1 m and ridge height of 4.7 m in theory. To test if the cleaning device can walk safely and stably on the arc frame of plastic greenhouses in practice and achieve a good cleaning effect, researchers did the walking velocity and cleaning effect experiment, the driving force experiment and the using effect experiment. The walking velocity and cleaning effect experiment’s results showed that: 1) the device’s walking was stable at the velocity of 6.6 m/min; 2) its average work efficiency could reach 6.6 m2/min; 3) the transmittance of plastic greenhouses was increased from 50.9% to 88.4% and from 49.0% to 88.9% after the cleaning of water and detergent, respectively; 4) the best cleaning water and detergent consumption were 1.2 L and 1.0 L per minute. The driving force experiment’s results indicated that the minimum driving force of the device was 69 N, which was greater than the theoretical calculation value and met the walking requests. The using effect experiment’s results showed that the transmittance increased by 46.7% when the greenhouse’ dip angle changed, which manifested this cleaning device had a good effect in use. This study solves the difficulty of plastic greenhouses cleaning, which can provide some reference for plastic greenhouses’ design.