Outer framework of multi-span greenhouse

The invention discloses an outer framework of a multi-span greenhouse. The outer framework comprises a transverse rod framework; stand column frameworks are evenly installed at the bottom of the transverse rod framework; connecting assemblies are evenly arranged on each stand column framework; positioning assemblies are installed at the bottom ends of one sides of the stand column frameworks; stepping motors are installed on one sides of the stand column frameworks on the outermost side; and pull rope winding rollers are arranged at the output ends of the stepping motors correspondingly and are connected through pull ropes. The outer framework is provided with the stepping motors, the pull rope winding rollers, the pull ropes, auxiliary rollers, guide blocks, folding sunshade nets, transverse moving plates and fixing sleeve pipes, each stepping motor winds and pushes the two ends of the corresponding pull rope through the corresponding pull rope winding roller, and therefore the fixing sleeve pipes and the tr