The invention relates to a water retaining plate. The water retaining plate comprises motors, pulleys, wire ropes, slope protecting plates and a water retaining plate; the motors and the pulleys are installed on door posts which are arranged on bilateral sides of a door; sliding channels are arranged on internal sides of the two door posts; the sliding channels extend to be under the ground; the underground depth of the sliding channels satisfies accommodation of the water retaining plate; two ends of the water retaining plate are embedded into the sliding channels; one ends of the wire ropes are connected to the motors and the other ends are connected with the water retaining plate after passing the pulleys; the number of the slope protecting plates is two; one ends of the slope protecting plates are connected to tops of the water retaining plates through hinges; the other ends of the slope protecting plates are provided with rolling wheels which are in contact with the ground. According to the water retaining plate which is hidden underground, vehicle traffic is not influenced, the water retaining plate is lifted when flood appears, vehicles can smoothly pass, and the water retaining effect is not influenced; the water retaining problem in transformer substation, workshops, factory buildings and courtyard gates is solved; the operation is simple; the water retaining effect is reliable; the vehicles are guaranteed passing and the water retaining effect is not influenced.