The present invention provides a water engineering quality-dividing system activated water saving device which comprises a filter that is provided with a water inlet, a water outlet and a filter element. The invention is characterized in that the input end of the filter is installed with a triplet reversing valve (1). A first end (2) of the triplet reversing valve is connected with the water source. A second end (3) is directly communicated with a first water outlet (4). A third end (5) is connected with a water inlet pipe (6) of filter. The device according to the invention adopts an original multipath quality-dividing water supply mode and can select tap water or quality-divided water according to the requirement of user. Not only can the user be provided with the water with different purifying effects, but also the increase of water discharge efficiency and service lifetime prolonging of filter are facilitated. Furthermore various minor elements or additives which are necessary forhuman body are added in different quality-divided water discharge channels according to the requirements of uses at different areas for facilitating the health of human body. The device and the technique of the invention are novel internationally. Not only is the using facilitated, but also the environment protection and the water saving of the whole society are promoted.