Abstract: To enhance the technical level of secondary equipment joint debugging in smart substations and ensure their stable operation, this paper elaborates on the fundamental concepts and core principles of secondary equipment joint debugging. Based on theoretical analysis, it takes a newly constructed smart substation project as an example to design the implementation process of key joint debugging technologies. This includes specific operational points for preliminary preparation, single-device basic verification, bay-level joint debugging, cross-bay and whole-substation joint debugging, and the evaluation of secondary equipment joint debugging effectiveness. The study shows that the maximum GOOSE/SV message transmission delay is 2.8 ms, meeting the requirement of ≤3 ms. The alignment rate between secondary and primary equipment reaches 100%, with all other core indicators meeting standards. The joint debugging of secondary equipment performs well, verifying the feasibility of the smart substation secondary equipment joint debugging technical solution and providing a practical reference for similar projects.