AIM: To investigate the effect of ofloxacin eye drop on bacterial culture of the conjunctival sac in senile cataract patients. METHODS: Thirty cases (60 eyes) with senile cataract were randomized into two groups: the control group (15 cases, 30 eyes) and the ofloxacin group (15 cases, 30 eyes). The ofloxacin group received 3g/L ofloxacin eye drop five times per day and one drop per time. Bacterial culture was done before treatment and at day 1, 2 and 3 of treatment. RESULTS: The cumulative score of bacterial colonies in the conjunctival sac for the control group was 51, 51, 33, and 42 respectively, and for the ofloxacin group, 51, 30, 9 and 0 respectively. Paired t-test showed a P value of 0.043 at day 3 of treatment. The positive rate of bacteria in the conjunctival sac for the control group was 60%, 60%, 40%, and 50% respectively, and for the ofloxacin group, 60%, 30%, 10%, and 0% respectively. The Chi-squared test showed P<0.01 at day 3 of treatment. CONCLUSION: Using ofloxacin eye drop for 3 days before surgery can eliminate the bacterial flora of the conjunctival sac in senile cataract patients.