Toilet water tank component with gear-rack type flow regulating function

The invention discloses a toilet water tank component with a gear-rack type flow regulating function, which has the advantage that the water discharging amount can be freely regulated within 6 liters specified internationally. Prior to water discharge, a knob is adjusted, a rack is driven by a gear to move in a horizontal cylinder, a medium in the horizontal cylinder is exchanged by a medium in a vertical cylinder through a connecting tube, and the position of a float is adjusted to determine the final water discharging amount. When water is discharged, a flushing handle is pulled, the buoyancy disappears when the water level drops to the level of the float, and a water discharging valve is closed under effects of the gravity. The operation is simple, and significant water-saving effects can be achieved.