For a significant period in the future, vehicles with different levels of automation will share road resources, with connected vehicles capable of traveling in closely spaced platoons. In this study, a mixed traffic flow model considering connected vehicle platooning is proposed based on a Markov chain model. With numerical experiments, the effects of vehicle penetration rate and maximum platoon size on fundamental diagrams and lane capacity are investigated. The results indicate that the increasement of penetration rate of connected vehicles can significantly promote the capacity. In addition, there is a threshold value for the maximum platoon size. When the maximum platoon size is smaller than the threshold value, lane capacity will increase with the increasement of maximum platoon size. While if the maximum platoon size is larger than the threshold value, the capacity will decrease as the increase of the maximum platoon size.