The invention provides an external medicament composition for treating arthritis, which contains ketorolac tromethamine of a nonsteroidal antiinflammatory drug and an active ingredient of mycophenolate sodium of immune inhibitor. The invention proves that the mycophenolate sodium and the ketorolac tromethamine have good cooperation action, can achieve better treatment effect on the joint pain of arthritic patients, and can improve the healing rate.