Abstract: Objective:To explore the dynamic balance ability of single-foot and double-foot standing in individuals with unilateral functional ankle instability(FAI).Methods:Balancecheck dynamic balance instrument was used to assess the dynamic balance ability under singlefoot and double-foot standing for 32 individuals with unilateral FAI,18 individuals with bilateral FAI and 20 healthy individuals,among 60s double-foot standing testing,30s single-foot standing.ANOVA test was used to compare the balance ability among the three groups,while for the difference between the two sides within the group,paired t-test analysis was used,the significance level was set at 0.05.Results:When double-foot standing,there was significant difference in the dynamic balance indexes among the three groups(P<0.01);there was significant difference in Score and Grade between bilateral FAI group and unilateral FAI group(P<0.05).Under single foot standing,there was significant difference in the values of most dynamic balance indexes among the three groups(P<0.05);while there was significant difference in the values of Score and Grade indexes between the foot with ankle instability and the other foot in unilateral FAI group(P<0.05).Under single foot standing,there was significant difference in Score and Grade between bilateral FAI group and unilateral FAI group(P <0.05).Conclusions:Both bilateral FAI and unilateral FAI individuals' dynamic balance ability were weaker than healthy individuals,the bilateral FAI individuals' were even weaker;the dynamic balance ability of the injured side for unilateral FAI individuals was also slightly weaker than those of the uninjured side,while the single foot dynamic balance ability with unilateral FAI individuals had some symmetry.