Aiming at the problem of connectivity in Vehicular Ad Hoc Network (VANET), the evolution characteristics of connectivity characteristics for VANET were analyzed. Firstly, the number of connected components, connectivity probability and connectivity length were proposed to be used for the evaluation connectivity metrics for VANET. Then, based on Intelligent Driver Model with Lane Changes (IDM-LC), the VANET was set up through VanetMobiSim software. Finally, the relation of node communication radius and the average number of connected components, average connectivity probability and average connectivity length were given. At the same time, the statistical distribution of the number of connected components was also analyzed. The results show that number of connected components follows a normal distribution by using Q-Q plot and T-test. Moreover, the results also show that the statistical distribution of the number of connected components is independent of the node communication radius.