The effects of ultrasonic intensity,ultrasonic time,temperature,usage of catalyst and reaction time on the yield of conjugated linoleic acid were studied.The mathematic model of these factors to the yield was also established through uniform design.The product was characterized by ultraviolet spectroscopy and infrared spectroscopy.The results show that the factors of ultrasonic intensity,ultrasonic time,temperature,usage of catalyst and reaction time are all important to the yield of conjugated linoleic acid.Uniform experiments indicate that comparing with other factors,the ultrasonic intensity,in the range of 22.17~27.26 W/cm~2,doesn't play an important role in the reaction.Under the conditions of the experiments,the higher the temperature,the longer the reaction time and the more usage of catalyst,will yield higher production.To obtain desirable product,the mathematic model can be used in reality to select proper parameters.In comparison with the normal method,the process assisted by ultrasound can achieve higher yield under the same conditions;it can also reduce catalyst usage and shorten reaction time with the same yield.Spectrum analysis shows that the conjugation is reacted and the cis-trans configuration is the primary products.