The invention relates to an in-vehicle air pressure balance device with a noise reduction function. The device comprises a shell, two partition plates, an air inlet pipe, a transition pipe and a pressure reduction valve. An inlet and an outlet are formed in the shell, and an inner cavity of the shell is divided into a resonant cavity, an expansion cavity and an output cavity through the two partition plates; one end of the air inlet pipe is matched with the inlet and is communicated with the interior of a vehicle, and the other end of the air inlet pipe penetrates the two partition plates to be communicated with the output cavity; noise reduction holes are evenly distributed in the portion, located in the expansion cavity, of the air inlet pipe, and two ends of the transition pipe stretch into the resonant cavity and the expansion cavity respectively; the pressure reduction valve comprises blades and gratings, wherein the blades cover the outlet, and the gratings are used for supporting the blades; the pressure reduction valve is arranged at the position of the outlet, and is used for preventing air from flowing into the output cavity from the outer portion of the vehicle; and when the air pressure in the output cavity exceeds the large air pressure, the pressure reduction valve is opened, and therefore the air is allowed to flow to the outer portion of the vehicle from the output cavity. The air pressure inside the vehicle can be balanced, and meanwhile the noise transmitted to the interior of the vehicle from the outlet can be removed.