AIM: To investigate the influence of He-Ne laser on connective tissue growth factor (CTGF) expression and collagen formation of fibroblast in filtration site after trabeculectomy in rabbit, and to discuss the mechanism for preventing scar formation with He-Ne laser in vivo. METHODS: The upper nasal limbus area next to the upper rectus muscle in right eyes received 10 minutes He-Ne laser irradiation (200mW/cm2) every day for three days, the left eyes served as control. Twenty-four hours after the last irradiation, both eyes of the rabbits were took trabeculectomy surgery. The expressions of CTGF in the filtration area were tested on the 7th, 14th and 28th day after surgery and collagen density was tested on the 14th and 28th day after surgery. Each of the time point had 7 rabbits. RESULTS: The expression of CTGF was lower than that of the control group's on the 7th and 14th day after trabeculectomy surgery (P=0.01, P=0.005). When examined on the 14th and 28th day, the collagen density of irradiation group were significantly lower than that of the control group's (P=0.013, P=0.01). CONCLUSION: Pretreating the filtration area with 200mW/cm2 He-Ne laser may be helpful in preventing scar formation after trabeculectomy in rabbit, possibly due to downregulation of the expression of CTGF and collagen synthesis in fibroblasts. He-Ne laser may be developed into a new scar preventing method in filtration surgery.