Abstarct: Maintenance scheduling affect on life time of equipments and consequently profit of investment. Degradation degree of equipments is usually used as a criterion for maintenance scheduling. For optimal maintenance scheduling in addition the degradation degree of equipments importance degree of them must be considered. Importance degree of an equipment is defined as decrease in system reliability due to outage of the equipment. In this thesis both degradation degree and importance degree of equipments are considered in maintenance scheduling of 230 KV Toos power station equipments. To this end, first the importance degree of circuit breakers of 230 KV Toos power station is determined. Load reduction cost is used as a criterion for determining the importance degree of facilities. Then degradation degrees of the equipments are determined using fuzzy logic. Online tests are used to determine degradation degrees of the equipments. Next sensitivity of degradation degree of equipments to the online tests is studied. After that, importance and degradation degrees are combined to obtain a criterion for determining maintenance priority of the equipments. In this thesis linear combination of importance and degradation degrees are used. Sensitivity of maintenance priority of equipments to online tests is studied. Results obtained from the proposed method are confirmed by results obtained from system analysis.