Objective: To set up the animal model of precancerous lesion of rats' pancreatic acinar cellular cancer,and to learn estrogen's effect on this lesion's biological feature and K-ras gene mutation. Methods: male Wistar rats were injected Azaser-ine 30mg/kg(ip). Some rats received Estradiol-17 P Valerate(0.18mg/100g/2weeks, im) .4 months later, rats'pancreas were autopsied and K-ras gene mutation were detected by PCR-SSCP method. Results : The incidence of AACN were very high. The incidence of K-ras gene mutation was 42.1% in rats without estrogen and 25.6% with estrogen. Conclusion: Azaserine could induce precancerous lesion of rats' pancreatic acinar cancer successfully, K-ras gene mutation was early change during this process Estrogen could inhibit this precancerous lesion's happen and development to some degree.