Objective To choose the best retraction agent for the clinic by evaluating the gingival inflammation related to three kinds of retraction agents. Methods 40 maxillary premolars were divided into four groups according to the randomized block design: Ferric sulfate group, aluminum chloride group, epinephrine group, sodium chloride group（control group）, each 10 teeth, respectively used 25% AlCl3, 15.5% Fe2 （SO4）3, 0.1% HCl- epinephrine, sodium chloride as retraction agents. The quantity of gingival crevicular fluid（GCF） and the active level of aspartate aminotransferase（AST） in gingival crevicular fluid were measured before and 1, 3, 5, 7, 9 days after retracting gingiva by four kinds retraction agents. The changes of GCF were calculated. Results The change of the GCF from the smallest to the largest was sodium chloride, 0.1% HCl - epinephrine, 25% AlCl3 , 15.5% Fe2 （SO4）3. Compared withsodium chloride, only 15.5% Fe2 （SO4）3 in AST was the significant difference in the first day and the third day（P
