Considered the conditions that vary length and vary probability message share one FlexRay dynamic data frame. In this condition analyze the delay of FlexRay dynamic segment data frame. Base on the Markov Chain, Construct our model that uses the delay probability to measure the FlexRay dynamic delay. Spread model from one cycle to multi-cycle, and then use MATLAB simulates the model. The result shows that the model can react the process of FlexRay dynamic segment data.