The invention provides a water-saving indoor drainage system which is composed of a toilet horizontal branch pipe, a kitchen horizontal branch pipe, a balcony horizontal branch pipe, a sewage discharger, an odor-proof valve and the like. The height of a pouring board is slightly lowered and a cushion layer is thickened to lay the toilet horizontal branch pipe, the kitchen horizontal branch pipe, the balcony horizontal branch pipe, the sewage discharger, the odor-proof valve and the like into the same floor layer so as not to pass through the floor to enter other households. The indoor drainage system provided by the invention has the advantages of automatically-utilized waste water, water conservation, energy conservation, emission reduction, less expenditure, no odor and floor drainage while relieving nature, no stench returned from an sanitary appliance joint and a closestool, no blockage of the closestool, no blockage and water leakage and easy dredging of a pipe, less loss of room height and good appearance. The water-saving indoor drainage system is applicable to water drainage and conservation transformation of buildings such as houses, hotels, wards and the like, and the system meets the need of the water-saving society.