Abstract: Based on the conduction mechanism of triggered vacuum switch, an experimental scheme has been designed to study the switching-on process of long-gap triggered vacuum switch. The switching-on process and the factors affecting the conduction characteristics of long-gap vacuum triggered switch were discussed according to photos gained from high speed camera. The factors affecting the spark resistance of triggered vacuum switch were analyzed. The experimental results confirm that the spark resistance and delay time can be effectively reduced by shortening the rise time and enhancing the peak of trigger current. The conclusion of experiment verifies theoretical predictions.