Ankle joints play an important role in supporting humans standing and walking, but they are prone to be injured during movement. Therefore, rehabilitation treatment of ankle injury has attracted more and more attentions. There are some limitations for traditional training methods, such as the training monotony, the large human consumption and the difficulty to quantify the training effects. In this paper, a virtual reality-based training system for ankle joint rehabilitation is designed. By combining an aircraft roaming virtual reality game with the rehabilitation training, the subjects' enthusiasm during rehabilitation can be improved, which leads to positive effects on rehabilitation training. Training data is saved for quantitative assessment of rehabilitation. In addition, this paper proposes a rehabilitation assessment method based on multi-index fusion of kinematics and electromyography (EMG) signals. The method includes three indexes, namely, root mean square of EMG, joint activity and joint smoothness. Experimental results prove that the proposed indexes can distinguish the subjects' healthy side from the affected side.