The alkyl phosphate prepared by phosphorus oxychloride and fatty alcohol contained a large amount of hydrochloric acid but no chloride. So the content of phosphate mono- and diester couldn’t be determined by conventional method. In this paper the content of hydrochloric acid was determined by potentiometric titration at first, and then the conventional method can be used to detect the content of mono- and diester and phosphoric acid. In this way each component of the alkyl phosphate can be ascertained accurately. The method was verified simply and conveniently by verification test that could avoid extraction, recrystalli- zation and other cockamamie operation. It also had stronger application and good reproducibility.