Abstract: Different particle diameters and calcination conditions that affect active lime were investigated，and two evaluation indexes of activity of active lime were compared as well：activity degree method and carbonation rate（EDTA） method.Results showed when lime stone that was preheated at 700 ℃ for 1 h，and then calcined at 1 150 ℃，the lime that particle diameter between 1~2 cm had higher activity than that particle diameter between 4~5 cm；when the particle diameters were the same，the activity of lime that was calcined at 1 150 ℃ had higher activity than that was preheated at 700 ℃ for 1 h firstly and then calcined at 1 150 ℃.Activity degree method and EDTA method were used for determination of activity of lime respectively，and the results were basically in accordance with each other.

Key words: activity degree method, lime, limestone, carbonation rate