This paper suggests a protective effectiveness index as a performance index for the optimal or adaptive protection of a power distribution system. The setting rules are considered as a performance measure of every parameter and used as a primary evaluation element. The rules are categorized into three groups for the hierarchical evaluation. After all the parameters are evaluated, the device-wise, coordination-wise and system-wise protective effectivenesses are calculated, in turn. The proposed method is applied to a typical distribution network to show its effectiveness.