The construction of second-line ship lock extension projects generally adopts the mode of concurrent construction and navigation.Construction operations and ship navigation are highly coupled in time and space,making it difficult to assess navigation safety risks.To accurately quantify navigation safety risks,a risk assessment index system consisting of four first-level indicators and seventeen second-level indicators has been constructed.Combining the Markov chain Monte Carlo (MCMC) method with the technique for order preference by similarity to ideal solution (TOPSIS),a dynamic safety risk index model is established.The MCMC method is adopted to characterize the dynamic coupling relationships of uncertain indicators and generate stable system state samples.the TOPSIS method is used to calculate the safety risk index and classify risk levels.A case study was conducted on the construction of the separation dike section at the lock head of Xinba Second-line Ship Lock of the Hangyong Canal.The results show that the navigation safety risks of the project are mainly concentrated at the “general” level (accounting for 74.7%) and “low” level (accounting for 19.9%),indicating a reliable overall safety level.The construction period,ship traffic volume and wave height are the key uncertain factors affecting navigation safety,and the superposition of multiple adverse factors may cause the risk level to rise.The assessment index system and model proposed in this study can provide a scientific basis for navigation safety risk management and control of similar projects.