At presentthe testability models considering uncertain factors have the problems of high modeling complexitycomplicated structuredifficult hierarchical modelingweak learning abilityand poor expression of uncertain information.Oriented to electronic equipmenta hierarchical testability modeling method based on Bayesian network is proposed.The original Bayesian network model and the multi-signal flow graph model are taken as research objectswhose parametersstructural characteristicsadvantages and shortcomings are analyzed.According to their complementary relationship and testability modeling requirementsthe Bayesian network model is improved.The model replaces the fault and test relationship with the fault and signal relationshipand characterizes fault transmission by the connection between signal nodes.The models structure is determined by using the hierarchical structure of circuitsand the models parameters are established by using Bayesian networkwhose inference ability is used to calculate testability indexes.Amplification filter circuits are taken as an exampleand a model is built and used to calculate the testability indexesand evidence processing tests are conducted.Compared with the multi-signal modelsthe model can accurately calculate testability indexes with strong evidence processing abilitywhich verifies the effectiveness and practicality of the modeling method.