The invention relates to a deep foundation pit layered ladder section combined excavation method of a wide shallow river valley with a sand gravel thickness coverage layer. The method is characterizedin that a drainage ditch, a water collecting well and a water precipitation well are arranged at an inner part of a foundation pit before a sand gravel layer is excavated, and an elevation adjustingbody and an energy dissipation groove are arranged at a joint of the drainage ditch and the water collecting well; layered thickness and a partition position of the sand gravel layer are determined firstly, then layered partition excavation is carried out, and then a mortar protective layer is sprayed on a slope surface; layered loose blasting is sprayed on a rock stratum from top to bottom, and pre-crack blasting is adopted on the side slope part, a blasting working groove is arranged inside the protective layer, a horizontal main blasting hole and a horizontal auxiliary blasting hole are synchronously drilled, and then smooth blasting is carried out; a concrete cushion layer is immediately applied after the rock stratum is excavated; and finally a transverse reinforcement body, a transverse drainage body and a plain concrete layer are arranged on the slope of the foundation pit. According to the method, the cost of drainage of the foundation pit and a construction channel can be saved. the field construction efficiency and quality can be improved as well, and the influence on the surrounding environment can be further reduced.