Background: To investigate the 1-time success rate of probing alone and nasolacrimal duct probing combined with nasolacrimal injection of levofloxacin ophthalmic gel on congenital nasolacrimal duct obstruction (CNLDO) in young children. Methods: A retrospective case series was performed on 494 cases (647 eyes) of 3–12 month-old children with CNLDO between July 2014 and July 2015. Material obtained from the lacrimal sac was cultured to isolate infectious agents. Susceptibility testing was done. Children from 3–12 months of age who were found to be sensitive to Levofloxacin (n=493 eyes) were separated into two groups: 3–6 months of age (276 eyes) and 7–12 months of age (217 eyes). Each of the groups were then randomized into group A (138 eyes of 3–6 months of age; 102 eyes of 7–12 months of age) and group B (138 eyes of 3–6 months of age; 115 eyes of 7–12 months of age). Children in group A underwent nasolacrimal duct probing alone; those in group B underwent nasolacrimal duct probing plus nasolacrimal duct injection of levofloxacin and the efficacy of probing was evaluated. Results: The average detection rate of pathogenic bacteria in dacryocystitis was 75.1%, andStaphylococcus aureuswas found to be the main pathogenic bacteria (42.59%, 106 cases). Among children from 7–12 months of age, the 1-time success rate of nasolacrimal duct probing alone was 88.24% and the 1-time success rate of probing combined with nasolacrimal duct injection of levolfoxacin ophthalmic gel was 96.52% (statistical signiifcance, P=0.02<0.05). Conclusions: Most pathogenic bacteria (96.81%) were sensitive to levofloxacin. Nasolacrimal duct probing combined with nasolacrimal duct injection of levolfoxacin may improve the success rate of probing in children older than 6 months of age.