Objective To compare the effects of Nd:YAG laser under contact lens on after-cataract in terms of un-dilated pupils and dilated pupils.Methods A total of 92 patients with after-cataract (92 eyes) treated from May 2017 to February 2019 were divided into un-dilated pupils group (n=46) and dilated pupils group (n=46) by random number table.The un-dilated pupils group was given laser therapy without contact lens, and dilated pupils group was treated with laser contact lens after dilating pupils.The visual acuity, intraocular pressure, laser treatment time, laser irradiation energy, and complications in two groups were observed.Results There were no statistical differences in the visual acuity and intraocular pressure between the two groups before and after surgery (P>0.05).The difference in the visual acuity of the two groups was statistically significant before and after surgery (P<0.05).The treatment time and laser irradiation energy in the un-dilated pupils group were shorter than those in the dilated pupils group (P<0.05); There was no statistical difference in the incidence of complications between the two groups (P>0.05).Conclusion The effects of Nd:YAG laser under contact lens on after-cataract in terms of un-dilated pupils and dilated pupils are similar.However, un-dilated pupils treatment without laser contact lens can shorten operation time, decrease laser irradiation energy, and not increase risks of complications, which is relatively safe.