Abstract: OBJECTIVE To analysis the influencing factors of stability of compound libavirin oral liquid, and to build up a reasonable preparing method to improve the product’s quality. METHODS Use single factor tests to study the influences of preparing conditions, including intermediate product’s pH value, sterilizing temperature and metal ions, to the product’s quality, and to find out the best preparing conditions by the L9(3⁴) orthogonal tests. Then to test the product’s accelerated and long term stability. RESULTS The orthogonal test results showed that the intermediate product’s pH had the most significant impact on the sterilized products’ stability. The next influencing factor was the sterilizing temperature and the metal ions had the minimum impact. The best preparing method group was A₃B₂C₂ (intermediated product’s pH 7.0, sterilizing temperature 105 ℃/30 min and add 0.01% EDTA-2Na). CONCLUSION The compound libavirin oral liquid’s stability is associated with its intermediated product’s pH, sterilizing temperature and metal ions. The intermediated product’s pH and sterilizing temperature has the major impacts on the product’s stability. The final optimized preparing method is pH 6.9?7.0 of intermediated product, 105 ℃/30 min sterilizing temperature and adding 0.01% EDTA-2Na into the product. Thus to improve the product’s stability.