Multi span greenhouse is an economical greenhouse that is popular among users for its beautiful curved shape and low cost. The curved ceiling is beautiful and elegant, with a smooth line of sight. The structure uses less steel and has good insulation performance. The manufacturing cost is relatively low, making it an economical greenhouse suitable for most regions. Double layer film greenhouses are commonly used in northern regions, while single film greenhouses are more commonly used in southern regions. It can obtain maximum illumination in the visible light range of 0.4-0.7 microns. After the layer film is inflated, a thick airbag can be formed, which can effectively prevent heat loss and prevent the intrusion of cold air. The use of double-layer inflatable film can greatly improve the greenhouse insulation performance and save operating costs. The top of the covering material is covered with polyethylene drip free longevity film, with an outer layer that is UV resistant and an inner layer that is anti dew; Polyethylene drip free longevity film or polycarbonate hollow board can be used to cover the surroundings according to user needs.