OBJECTIVE To establish a new model of posterior capsule opacification (PCO) in rat, and detect the expression of alpha-, beta-, and gamma-crystalline gene. METHODS An extracapsular lens extraction (ECLE) was performed in SD rats. Eyes were enucleated and processed for light microscopy at various time-points. Semi-quantitive RT-PCR were performed to detect the expression of alphaA, alphaB, betaB1, betaB2, betaA2, and gammaD crystalline. RESULTS Immediately after ECLE, lens epithelial cells (LECs) were present in the inner surface of the anterior capsule and lens bow. 24 hours after surgery, LECs started to migrate toward the center of the posterior capsule. PCO was noted at first 3 days after ECLE, multilayered LECs were present throughout the lens capsule, and lens fibre differentiation occurred in peripheral capsular bag. All eyes showed development of clinically evident PCO and Soemmering's ring 7 days post-ECLE. 2 weeks after surgery, Soemmering's ring was even more significant. 1 month after surgery, all capsular bags were filled with new semitransparent lenticular structures, displaying an established equator with well differentiated bow regions. 2 - 3 month after surgery, new lenticular structures continue to increase in slower speed. The mRNA-expression quantity of alphaA, alphaB, betaB1, betaB2, betaA2 and gammaD crystalline increased gradually postoperatively. CONCLUSIONS PCO occurs soon after ECLE in SD rat, and express alpha-, beta-, and gamma-crystalline. This model appears to be valuable for studying the pathogenic mechanisms of PCO after cataract surgery or lens regeneration.