The invention discloses a mobile local air exhaust device. The mobile local air exhaust device comprises a moving vehicle body, wherein a sealing box is arranged on the vehicle body; an exhaust fan is arranged inside the sealing box; an air draft pipe penetrates through the sealing box and icommunicates with an air draft hole of the exhaust fan; an exhaust pipe penetrates through the sealing box and communicates with an exhaust hole of the exhaust fan; the other end of the air draft pipe communicates with an air draft cover; the other end of the exhaust pipe communicates with a main tail gas filtering device; and the air draft pipe adopts a space-adjustable connecting pipe. The mobile local air exhaust device can be moved to any open operating point positions lacking of local exhaust coverage, the space-adjustable exhaust pipe can effectively collect polluted air at open operating point positions more closely, and the high-power exhaust fan can improve the fluidity of air and more quickly feed the polluted air at the open operating point positions to the main tail gas filtering device in a testing hall, so that the requirement on safety protection in open operation is met, and the environment assessment of the open operating point positions is guaranteed to reach the standard.