A wagon and a car body assembly thereof are provided. The car body assembly includes at least two bogies, an underframe and a car body both supported on the two bogies, the car body includes a middle car body, and a discharge opening of the middle car body is arranged between the two bogies, and at least one end of the middle car body is further provided with an end car body, and a predetermined space is defined above the respective bogie by adjacent end walls of the middle car body and the end car body.