Tail gas collecting box for detecting PM (Particulate Matter) 2.5 content of automobile tail gas

The invention belongs to the field of automobiles, and particularly relates to a tail gas collecting box for detecting the PM (Particulate Matter) 2.5 content of automobile tail gas. The tail gas collecting box comprises an inner box, an outer box, a gas inlet pipe, an exhaust pipe, a temperature sensor, a humidity sensor, a PM2.5 detecting instrument and a vehicle-mounted inverter, wherein the tail gas collecting box is arranged in an automobile trunk; the inner box is arranged in the outer box; one end of the gas inlet pipe is connected with the automobile exhaust pipe through a plastic pipe; the other end of the gas inlet pipe passes through the outer box to extend into the inner box; one end of the exhaust pipe is arranged in the inner box, and the other end of the exhaust pipe passes through the inner box and the outer box to be arranged in air; the temperature sensor, the humidity sensor and the PM2.5 detecting instrument are arranged between the outer box and the inner box; a heating sheet is attached