Vehicular Ad Hoc Networks (VANETs) can provide safety and non-safety related applications and services to improve the passenger safety and comfort. Due to the space and time dynamics of moving vehicles, network connectivity is an important performance metric to indicate the quality of the network and the user's satisfaction. Grouping vehicles into platoons in the highway can improve road safety, reduce fuel consumption, and decrease traffic congestion. In this paper, we study the connectivity characteristic of platoon-based VANETs. The connectivity probabilities are analyzed for the Vehicle-To-Vehicle (V2V) and Vehicle-To-Infrastructure (V2I) communication scenarios. The relationships between the connectivity probability and the key parameters are investigated, including the traffic density, the coverage of the ordinary vehicle, the coverage of the platoon, the coverage of the Road Side Unit (RSU), the distance between two adjacent RSUs and the ratio of the platoon in the VANET. The results can help the transport system designer to control the traffic on the highway to satisfy the connectivity requirement. Analysis results show that the connectivity probability can be significantly improved when there are platoons in a network. © 2014 IEEE.