AIM:To observe the treatment efficacy of 1-6 months age infantile congenital nasolacrimal duct obstruction(CNLDO) and dacryocystitis by probing of lacrimal passage and the lacrimal secondary adhesion occurrence. And the children were divided into 1-3 months age group and 3-6 months age group, to compare the efficacy and the incidence of adhesion to determine the best opportunity of probing treatment. METHODS:Totally 288 cases of 1-6 months age with CNLDO and dacryocystitis were randomly selected from June 2007 to December 2011 in our hospital, including 150 male cases, 138 female cases,230 unilateral cases and 58 bilateral cases.The age distribution was 30-180 days, an average of 86.66±40.55 days. The children were divided into 2 groups according to age: first group of 1-3 months age,173 cases(observation group); second group of 3-6 months age, 115 cases(control group). Treatment methods of two groups were the same, with 1% tetracaine for topical anesthesia of the punctum, appropriate expansion of the inferior lacrimal punctum, routine operation of irrigation and probing of the lacrimal passage using round-head flushing probe with external diameter of 0.5mm or 0.6mm and measuring hole , but the probes included angle with the horizontal line maintained in 75°-85°after its entering into the lacrimal sac, and the probe retained for 30-60 minutes to dilate the lacrimal duct after successful probing of the lacrimal passage. The children took prone position for removal of the probes and the lacrimal residual secretion and cell debris were rinsed as completely as possible.The lacrimal adhesion was recorded in the process of probing of lacrimal passage. The lacrimal passage was rinsed again 4-6 days after operation to observe and consolidate the curative effect. Followed up for 3-6 months,the two groups were compared with curative effect and lacrimal secondary adhesions. RESULTS: The cure rate of first group was 98.1%, lacrimal secondary adhesion rate was 29.3%. The cure rate of second group was 82.6%, lacrimal secondary adhesion rate reached 70.3%. Through statistical analysis, the effect of two groups had significant difference, 1-3 months age group was significantly better than 3-6 months age group; the formers lacrimal secondary adhesion rate was lower than the latters. CONCLUSION:For CNLDO and dacryocystitis,the treatment effect of probing is very good in advance to 1-3 months age.The longer condition, the more lacrimal secondary adhesion opportunity, the lower efficacy. Previous claim was lacrimal passage probing after 6 months age.Through clinical observation, the author thinks that 1-3 months age is the optimal probing time, suitable for wide popularization and application in basic level hospital.