The safety analysis model of critical system is essentially a mixed model of both discrete variables and continuous variables.The traditional analysis methods can only deal with the system based on discrete distribution or exponential distribution

so these methods are incapable of analyzing the safety of the hybrid system.To solve the problem

this paper presents a novel safety analysis method of hybrid system on hybrid Bayesian network(HBN).First

by using the Dirac function and unit step function to represent the deterministic relation and timing sequence of nodes in DFT respectively

we convert the DFT into a Bayesian network(BN).Second

The HBN with

k

-piece and

n

-degree polynomials is propo

sed to represent the DFT

in which the different failure distributions of nodes are fitted by piecewise polynomial functions.Finally

the inference algorithm of HBN is proposed.The experimental results show that the presented method can effectively solve the safety analysis of hybrid system.