The invention relates to an online evaluation system for secondary equipment of an intelligent substation. The system comprises a master-station evaluation level and a transformer substation evaluation level, wherein the master-station evaluation level comprises an evaluation master station, the transformer substation evaluation level comprises a plurality of evaluation sub-stations which are arranged in all transformer substations respectively and multiple evaluation objects, corresponding to the evaluation sub-stations, of the relevant secondary equipment, the evaluation sub-stations are in communication with the corresponding multiple evaluation objects respectively through three-in-one network interchangers and communication lines, so that the evaluation parameters of the evaluation objects are collected, and the master station is in communication with the evaluation sub-stations through communication networks respectively so as to obtain the evaluation results of the evaluation sub-stations. The online evaluation system for the secondary equipment of the intelligent substation has the advantages that due to the fact that the online monitoring function of a monitoring system in the intelligent secondary equipment in the intelligent substation is used, in this way, excessive maintenance can be avoided, the workload of maintenance personnel is reduced, maintenance cost is reduced, and evaluation accuracy is extremely high.