The invention discloses a transformer fault diagnosis analysis method based on a bayesian network. The method includes the specific steps: step 1, determining transformer oil chromatography property variables Y = { Y1, Y2, Y3... Yn } and fault type variables D = { D1, D2, D3... Dm }, wherein yi is a value of Y1, dm is a value of Dm, using characteristic gas of a transformer oil chromatography as the transformer oil chromatography property variables, and using transformer fault types as the fault type variables; step 2, determining classification models, structural parameters and probability parameters of the bayesian network according to the transformer oil chromatography property variables and the fault type variables; and step 3, determining the transformer fault types by utilization of a connection tree algorithm.