Gasifier is the main equipment of CWS gasification system. In order to study the influence of gasifier failure on gasification system, a dynamic risk assessment method based on dynamic Bayesian network and risk matrix is proposed in this paper. Taking the gasifier failure as an example, the dynamic Bayesian network model of the gasifier was first established, and the prior probability of the root node event was calculated by combining the fuzzy evaluation method, and the dynamic Bayesian network was introduced to calculate the posterior probability. Then, based on the principle of analytic hierarchy process (ahp) and Borda, a comprehensive risk assessment for gasifier failure was established, and maintenance factors were introduced to predict the risk trend of the gasifier after maintenance and draw a dynamic risk matrix. The results show that the risk of the system decreases after the maintenance factor is introduced, which proves that the maintenance factor has a positive effect on the system and guarantees the production capacity of the system