Abstract: Content of available calcium oxide in lime was determined by potentiometric titration using HCl standard solution as titrant. Conditions of titration were optimized and given as follow: ① acidity at endpoint of titration: pH 7.00; ② maximum rate of titration: 10 mL·min-1; ③ minimum rate of titration: 100 μL·min-1; ④ delay time: 5 s. The proposed method was applied to the analysis of lime sample, and the results obtained were checked quite well with those obtained by manual titration. Values of RSD′s (n=5) were found in the range of 0.10%-0.19%.