The invention discloses a foundation pit side wall covering protective device for civil engineering construction. The foundation pit side wall covering protective device comprises a foundation pit, aside wall protective device, an outer transverse fixing device and an outer oblique fixing device. A built-in water pipe is arranged in a supporting baffle, the side walls of the foundation pit can beeffectively supported and protected, the water accumulation problem of the interior of the foundation pit can further be handled in time, work that water pumping pipes need to be repeatedly laid formultiple times when accumulated water of the foundation pit is treated is avoided, the accumulated water pumped out from the foundation pit can be collected into an external water treater to be recycled again, and thus energy conservation and environmental protection are achieved; additionally, when connecting plates are set up in the foundation pit, only a sliding connecting block needs to be placed in a built-in groove to slide down, and then the different fixing devices are selected according to the different connecting plates; the transverse connecting plate selects the outer transverse fixing device, and the oblique connecting plate selects the outer oblique fixing device; and the fixing devices fix firmly and are quickly mounted, the time and labor are saved, the setting up time canbe greatly reduced, and the setting up efficiency is improved.