The invention discloses an in-vehicle air purification system for purification through natural airflow. The in-vehicle air purification system comprises an air collection hood, a vacuum suction cup, afirst support, a main air pipe, a flow-dividing valve, multiple branch air pipes, an air purifier, a storage battery, a first switch, a second switch, a gear, a rack, a reset spring, a touch rod, a second support, a windmill, a guide rail, a third support, a slide block, a first fixed block and a fourth support; a heating structure is fixed inside the main air pipe and comprises a protection hood, a heating rod, a third switch and a fixed rod, the upper end of the fixed rod is connected with the inner wall of the main air pipe, the lower end of the fixed rod is connected with the upper end ofthe protection hood, the protection hood is of a net-shaped structure, the heating rod is installed in the protection hood and is connected with the storage battery through the third switch, the third switch is fixed to the outer wall of the main air pipe, and a drying layer is arranged on the inner wall of the main air pipe and is filled with desiccant. The in-vehicle air purification system forpurification through the natural airflow has the technical advantages of being reasonable in system design and low in system energy consumption, and reducing the in-vehicle air purification cost.