Abstract: Through testing the cooling fan vibration and balance degree before and after ash cleaning on the testbed, the cooling fan abnormal vibration of Beijing Daxing International Airport Line vehicles is detected as the dust accumulation on the impeller. The operation environment of this line is complicated, affected by road transportation, civil engineering, land reclamation and farming along the line, there are plenty dust, silica gel and other particulate matters in the air, all of these are very likely to cause dust accumulation on the cooling fan impeller of vehicle traction converter and leads to abnormal vibration. Finally, the maintenance measures for current stage and follow-up improvement suggestions for vehicle traction converter cooling fan are put forward.