The invention belongs to the field of fresh air equipment, and discloses a fresh air distribution box, which comprises a box body, an air inlet round connecting pipe and socket-and-spigot flat connecting pipes. The box body is arranged horizontally, and is provided with a left straight side, a rear straight side and a conical arc; the rear end of the left straight side is connected with the left end of the right straight side; the left straight side is perpendicular to the right straight side; the front end of the left straight side is connected with the right end of the rear straight side through the conical arc; a plurality of socket-and-spigot flat connecting pipes are arranged at the left straight side and the lower straight side of the box body; the air inlet round connecting pipe is arranged at the top end of the box body; and an inner sunken circular arc transition gradually-wide pipe is arranged between the air inlet round connecting pipe and the box body, and is used for reducing the impact of an air flow on an inner bottom surface of the box body, so that the air flow gently enters the box body. According to the distribution box provided by the invention, the flow separation of air in the box body can be directly influenced, the direct impact of the air flow is improved, an air flow vortex and a speed cavity area in the box body are eliminated, and the flow rate of an outlet of each flat pipe is uniformly adjusted.