The invention discloses a sealing sound insulation method of a rail traffic vehicle. The method comprises the steps that a sealing airbag is arranged on the contact portion of a guest room door and avehicle body; after the guest room door is closed, the pressure inside and outside the vehicle is detected, a real-time pressure difference inside and outside the vehicle is obtained, and according tothe real-time pressure difference, an actual preset pressure value required by the sealing airbag corresponding to the vehicle is obtained; a real-time pressure value in the sealing airbag is detected; by comparing the real-time pressure value with the actual preset pressure value, the pressure of gas entering the sealing airbag is controlled, so that the pressure in the sealing airbag reaches the actual preset pressure value. According to the method, by controlling the pressure of the gas entering the sealing airbag in real time, the pressure of the gas in the sealing airbag is changed alongwith the pressure difference inside and outside the vehicle, and accordingly the rail traffic vehicle has good sealing sound insulation performance when driven in an open wire or tunnel environment.The invention further discloses a sealing sound insulation system for implementing the sealing sound insulation method and the rail traffic vehicle with the sealing sound insulation system.