The present invention provides a water filling closet pan. The water filling closet pan can perform closet pan flushing even when power is cut off. The water filling closet pan is characterized by comprising a basin portion, a drain elbow portion, a washing water supply unit, a control portion, and an operation portion, wherein the drain elbow portion is connected with the basin portion to form and ponding is formed; the washing water supply unit is drive by supplied electric power and supplies power for the basin portion; the control portion employs an emergency power supply to carry out electrical drive for the washing water supply unit when the power is cut off; the drain elbow portion is provided with a moving portion, which drives the drain elbow portion to carry out a mechanical change to keep the water level in the basin higher than an original water level; and the operation portion works according to the operation of a user, and sends a operation signal to the control portion while drives the moving portion to work according to the operation of the user when the power is cut off, the control portion drives the washing water supply unit to work and supply water to the basin portion on receiving the operation signal.