Abstract: As an important component of the electrical controlling systems, contactors should have the reliability of 100% within the scheduled time limit, so their reliability has aroused wide attention at home and abroad. Aiming at the failure phenomenon of contact welding of the contactors in a type of airplanes, some typical contactors were studied. The mechanism and cause of the contact welding after long-term heavy load work were analyzed. From the perspective of the maintenance and reparability, based on the actual state of the contactors, and combined with the overhaul of the aircrafts, it is suggested that the contacts should be ground and polished to reduce the contact resistance of the contacts and suppress the trend of contact wear. This method breaks through the bottleneck of contactor repairing, the reliability of the contactors and electrical controlling systems has been improved.