Objective: To study the early growth response gene-1 (EGR1) on the inflammatory response of lens epithelial cells (LECs) and epithelial-mesenchymal transition (EMT) after cataract surgery in mice. Methods: In this experimental study, 10-16 week-old EGR1 knockout mice (EGR1-/-) and wild-type mice (WT) were chosen for cataract surgery, and were sacrificed at 0 h, 3 h, 24 h, 48 h, 72 h, 4 d, and 5 d after modeling. The eyeballs were harvested for frozen section. Immunofluorescence staining was used to observe the expression of the EGR1 protein, CD11b, LCN2, CXCL1 and αSMA in the lens capsule and the fluorescence intensity was quantified by Image J. A paired t-test and one-way analysis of variance were used for comparison between groups and within groups. Results: The expression of the EGR1 protein in LECs after modeling in WT mice was up-regulated, as well as the expression of the inflammatory markers (CD11b, LCN2 and CXCL1). No difference in the level of EGR1 protein was observed in EGR1-/- mice after modeling, and the levels of CD11b, LCN2 and CXCL1 in the EGR1-/- mice were significantly lower than those in the WT mice (all P<0.01). In addition, the expression of αSMA (a marker of EMT) and the number of tangible cells in the lens capsule of EGR1-/- mice were also significantly less than those of WT mice (72 h, 4 d and 5 d after modeling, all P<0.05). Conclusions: Cataract surgery canactivate EGR1 in LECs at an early stage after surgery. Activated EGR1 participates in regulating the inflammatory response and the EMT of LECs. Knocking out EGR1 can reduce the above-mentioned inflammatory response and EMT.