The invention provides an intelligent substation digital secondary loop online state evaluation method. The method includes the following steps that: a digital secondary loop object model is constructed; key nodes of intelligent substation digital secondary loop state evaluation are determined; the state evaluation indexes of each key node are constructed; corresponding evaluation weight coefficients are established for each key node evaluation index; the online state monitoring of digital secondary loop state evaluation indexes is realized on the basis of relay protection, a switch and secondary equipment state self-test and online monitoring; and the state evaluation models and algorithms of various digital secondary loops are established, so that the online state evaluation of each digital secondary loop of an intelligent substation is realized. With the method adopted, the states of the nodes on the digital secondary loops of the intelligent substation can be monitored and evaluated, the detection of weak links on each digital secondary loop of the intelligent substation can be facilitated, and the health states of the entire digital secondary loops are comprehensively evaluated.