Background: Chronic ankle instability (CAI) is very common disease. Strength exercise, balance exercise, and proprioceptive exercise were used to improvement of function for CAI. Isokinetic strength and balance are related to functional movement of lower extremity. Objectives: The purpose was to analyze the effect of muscle strengthening exercise, balance exercise, and proprioceptive exercise on isokinetic strength and balance in young adults with CAI. Design: Randomized controlled trial. Methods: The subjects were 30 young adults with CAI. The subjects randomly divided into three groups: strengthening exercise, balance exercise, and proprioceptive exercise. They performed each exercise for 20 minutes, three times a week for four weeks. They measured isokinetic strength of dorsiflexor and plantar flexor of 60°/sec and 120°/sec, static and dynamic balance before and after exercise. Results: The isokinetic strengths of dorsiflexor and plantar flexor of 60°/sec and 120°/sec were significantly higher in the strengthening exercise group than in the balance exercise group. The static and dynamic balance was significantly higher in the balance exercise group than in other two groups. Conclusion: Strengthening exercise, balance exercise, proprioceptive exercise can improve the muscle strength for CAI. Strengthening exercise and balance exercise can more improve balance than proprioceptive exercise for CAI.