The invention discloses a urea solution tank filling assembly used for an SCR system. The urea solution tank filling assembly comprises a tank cover and a filling opening, the filling opening is formed in a urea solution tank, and a chain is connected between the filling opening and the tank cover. The tank cover comprises an upper outer cover body and a lower outer cover body, a ventilation cavity is formed in the center of the lower outer cover body, a plurality of ventilation holes are formed in the bottom of the ventilation cavity, ventilation film is arranged at the portion, located above the ventilation holes, of the ventilation cavity, a plurality of ventilation grooves are formed in the top of the lower outer cover body, the top of the lower outer cover body is connected with the interior of the upper outer cover body, the bottom of the lower outer cover body is connected with the filling opening, one end of the chain is connected to the top of the upper outer cover body in a rotatable mode, the other end of the chain is connected to the filling opening, and the filling opening is of an integrated structure. The urea solution tank filling assembly is convenient to assemble, and normal rotation of the tank cover can be guaranteed; in addition, expansion, caused by the fact that gas can not be effectively removed, of a tank body can be effectively prevented, and normal running of the system can be guaranteed.