The invention discloses a multifunctional tap water dechlorination device. The whole device comprises the multiple parts of a dechlorination cavity body, a connecting port, speed variation grids, a functional box and a buffering box, the connecting port, the speed variation grids, the dechlorination cavity body, the function box and the buffering box are sequentially connected from top to bottom,wherein the connecting port is connected with a water tap, tap water from the water tap passes through the connecting port and flows into the speed variation grids, multiple small holes are formed inthe speed variation grids, convective diffusion is formed after the tap water passes through the speed variation grids, then the tap water flows into the dechlorination cavity body and flows into thefunction box after dechlorination filtering is conducted on the tap water by the dechlorination cavity body, multiple additive substances with different functions are placed in the functional box, functional substances are carried by the tap water flowing out of the functional box, and the tap water is buffered by the buffering box and smoothly flows out. According to the device, the functional substances can be added according to the demand of tap water with higher quality of a user on the basis that the tap water is completely purified.