Studying the problems of power system planning, equipment selection and fault diagnosis, a new method for reliability evaluation of main electrical connection based on fault tree and elements importance analysis is proposed. The fault tree analysis method is used to convert the system topology into elements logical relations, which simply and intuitively reflects the reason of system failure. Selecting the reliability basic characteristics, comparing the structure importance, probability importance, and criticality importance of elements to identify the weak part of the system, then the reliability of main electrical connection is evaluated qualitatively and quantitatively. Through a case analysis of bridge-circuit configuration, three electrical elements importance were calculated and sorted respectively, and the influence of elements combination on the evaluation results was discussed, thus the rationality of the method is verified.