Objective: Ankle sprains occur during landings from heights, with inversion sprains. This study aims to investigate the kinematic and electromyographic characteristics among people with and without chronic ankle instability (CAI) during landing from different heights to a trapdoor device, and to analyze the differences in movement patterns between the two groups under ankle inversion perturbation, thereby providing theoretical support for optimizing landing strategies and preventing injuries. Methods: Twenty-five CAI and 25 non-CAI were recruited to land from heights of 16 cm and 30 cm to a trapdoor device, which tilts inward by 24° and forward by 15° to simulate the foot position during ankle inversion sprain. Kinematic and electromyographic data were collected. Results: The peak ankle inversion angle was greater in the CAI group than non-CAI group (P=0.003), and the peak ankle inversion angles decreased in both groups with increasing heights (P=0.035). In the CAI group, the peroneus longus muscle activation level was lower in the pre-activation phase (P=0.019) and landing phase (P=0.046), and the rectus femoris muscle activation level in the CAI group was greater (P=0.026), and the tibialis anterior activation level (P=0.015) in both groups increased with increasing height. The onset of activation of the peroneus longus was later in the CAI group than non-CAI group (P=0.025); the activation onset of the medial gastrocnemius occurs earlier (P=0.016). With the increasing heights, activation of the rectus femoris was delayed (P=0.017). Conclusion: The CAI group exhibits impaired ankle motor control and abnormal muscle activation patterns during landing from different heights. Rehabilitation training should focus on strengthening the peroneus longus and other stabilizing muscles to enhance landing stability and reduce the risk of ankle sprains.