Abstract: To describe complexity and instability of traffic flow operation in weaving area of roundabout,a microscopic cellular automata model was applied to simulate traffic laws. Firstly, based on the roundabout 's circular structure and directions of flow,a hexagonal cellular space with multi-value cellular state instead of traditional rectangle was built. Then the cellular rule based on improved gapacceptance theory was proposed to analyze the capacity of weaving areas. Finally, the numerical simulation was made by using MATLAB software. The simulation results show that the environment of hexagonal space can simulate the operation of traffic stream in weaving areas,in addition,the improved cellular rules can accurately describe the change curve and volatility of traffic capacity in weaving areas.The research results provide a fundamental basis for signal control and coordinative optimization in roundabouts.