A rationed water outlet device with a variable water flow volume includes a process control module including an outlet valve, a flow meter, a control chip, and an encoder that includes an unlimited outlet gear and a plurality of rationed outlet gears which are switchably connected to the outlet valve to provide respectively, when engaged, an unlimited water flow volume or a selected rationed water flow volume from among a plurality of rationed water flow volumes, and that is electrically connected to the control chip to provide gear selection information; a volume option switch that is rotatably linked to the encoder for engaging the unlimited outlet gear or one rationed outlet gear; and an outlet control switch that is independent of the volume option switch and that is engaged after the volume option switch is engaged.