Objective: To investigate the compounding of diclofenac sodium with hydroxypropyl β-cyclodextrin. Methods:The compounding was assessed by UV absorption spectroscopy and differential scanning calorimetry. The compounding rate was measured by phase solubility diagram. Results: The analyses showed the 1:1 (guest versus host) compounding ratio of diclofenac sodium to hydroxypropyl β-cyclodextrin. The solubility of diclofenac sodium was increased from 9.78mg·mL~(-1) to 52.2mg·mL~(-1). Conclusion : The irritation of diclofenac sodium to muscles may be reduced due to the higher solubility after the compounding.