To study the impact of car-motorcycle collisions on head injuries to motorcycle riders and passengers. 33 typical car-motorcycle collision cases were selected from the National Automotive Sampling System (NAIS) database. Using PC-Crash 12.0 software, a multi-body kinematic model was established. Firstly, a collision simulation model was developed for a real and representative car-motorcycle collision case to validate the model's effectiveness. Based on this validated model, simulation experiments were conducted to analyze the kinematic response processes of motorcycle riders and passengers under different collision scenarios. Then, the paper analyzed the impact of factors, such as vehicle speed, collision location, and collision angle on the head injuries of motorcycle riders and passengers. The results indicated that the head HIC values of the riders and passengers decreased with increasing speed of the two-wheeled motorcycle in the left-side crash condition. Moreover, in mid-section collision scenarios where the Sedan's speed was high and the motorcycle's speed was low, the head injuries to both the riders and the passengers were more severe, with the passengers sustaining more severe head injuries compared to the riders. Collisions on the right-side result in the most severe overall head injuries for both the riders and the passengers. For larger collision angles, the riders' head injuries were greater than the passenger in both mid-section and right-side collisions, In the right-side collisions, the injuries of the riders were particularly severe.