The invention discloses an online monitoring and intelligent diagnosis method for secondary overhaul safety precautions of a transformer substation. The online monitoring and intelligent diagnosis method comprises the following steps of 1, establishing a realization environment; 2, recognizing a safety precaution state change, determining whether a safety precaution process is already performed or not, if so, performing anti-misoperation intelligent diagnosis, or otherwise, recognizing a safety precaution process type firstly, and then performing anti-misoperation intelligent diagnosis; 3, performing alarm visualized exhibition according to an anti-misoperation intelligent diagnosis result, starting a safety precaution completion timer firstly, and then updating a state variable into a safety precaution sequential database; and 4, determining whether safety precaution completion is recognized or not, if not, returning to the step 2, if so, deleting the safety precaution completion timer, generating an online monitoring report and returning to the step 2; when the safety precaution completion timer is triggered manually, deleting the safety precaution completion timer, performing safety precaution anti-misoperation leakage examination, generating an online monitoring report and returning to the step 2; and when the safety precaution completion timer is triggered, performing safety precaution anti-misoperation leakage examination, generating an online monitoring report and returning to the step 2.