Objective To investigate the general clinical features of iris synechia formation after extraction of congenital cataract in the first year of life; to determine its relationship to the risk factors. Methods This was a retrospective clinical study. Sixty -two eyes of 33 patients with congenital cataract were evaluated retrospectively between January 2005 and December 2008 based on clinical records. The patients were divided into two groups according to their age at the time of surgery: group A ≤6 months old and group B >6 months old (≤12 months). All operations were performed under general anesthesia. A scleral tunnel approach was used with bimanual lens aspiration. Posterior capsulorhexis and anterior vitrectomy was performed on all infants without intraocular lens implantation. The incidence, time of appearance, location and scope of iris synechia formation were observed. Results Of the 62 eyes, iris synechia formation occurred in 31 eyes after surgery, with a 50% incidence rate. The incidence of iris synechia formation for groups A and B was 60.0%(24/40) and 31.8%(7/22), respectively, after infantile congenital cataract surgery. There was a statistically significant difference in the incidence between the two groups (χ2 =4.509, P<0.05). Synechiae occurred in 11 eyes (35.5%) within 2 weeks,and in 22 eyes (71.0%) within 1 month. Twenty-five eyes (80.6%) developed iris synechia in the superior part of the iris. The adhesion scope of 25 eyes (80.6%) was smaller than a quadrant, and when the severity of iris synechiae was measured in hour units, there was a statistically significant difference between the severity of the two groups [group A, (2.35 ±3.21)hours; group B, (0.77 ± 1.41 )hours; t =2.187, P<0.05]. Regarding complications, 7 eyes required pupilloplasty in the secondary IOL implant operation, 8 eyes had fibrin exudation postoperatively, and there was a recurrence of iris synechiae in 6 eyes. However, there was no similar complication in the non -synechiae eyes. The difference was statistically significant