Abstract: A water refilling control mechanism for a water tank comprises a main float sliding along an inlet pipe and further having an extruder located at the bottom thereof for connecting with an extension bar and further connecting to a supporting bar and a water valve on top of the inlet pipe. The main float further includes a dual-stair-shape valley atop to accommodate an auxiliary float having a restraint arm with its upper end connecting with a restraint cam located on top of the inlet pipe. By providing a C-shape end to the restraint arm connected engaging the restraint cam with an extruding arm, the auxiliary float can be restrained in the valley by a bump at the lower end of the restraint arm and can be rotated clockwise to release the main float as the water level reaching a substantial height.