The utility model discloses a mobile multichannel big air duct air volume measuring system which comprises a measuring element, a data collecting processing system, a drive control circuit, a drive motor, a drive connecting piece and a signal switching circuit. The measuring element is composed of a total pressure tube, a static pressure tube and a temperature measuring device. The motor control signal output end of the data collecting processing system is connected with the drive motor through the drive control circuit, the drive motor is connected with the drive connecting piece, the measuring element is arranged on the drive connecting piece, and the signal output end of the measuring element is connected with the signal input end of the data collecting processing system through the signal switching circuit. The mobile multichannel big air duct air volume measuring system overcomes the measuring difficulty caused by a short straight tube section, a low flowing speed, a complex flowing field and the like of a big cross-section air duct, so that the measuring accuracy is increased, the windage resistance of the measuring device is small, the problem that the windage resistance of the measuring device is large due to the fact that multiple channels are arranged to be too close can be solved, and normal operation of equipment is not influenced.