Abstract： Objective To observe whether corydalis alkaloid preprocessing can narrow myocardial infarction range of rat's myocardium.Methods All 30 adult rats with clean level were randomly divided into six groups(high,middle and low doses of corydalis alkaloid groups,classical ischemia pre-processing group,model group and sham operation group,n =5 each group).The heart was separated from body,and was ligated and retrogradely poured into 2％ Evan's blue through aorta,and then myocardial non-ischemic area and ischemic area,infracted area and ischemia non-infracted area were separated.The myocardial ischemia area and myocardial infarction area were compared among six groups.Results ①There was no myocardial ischemia in the sham operation group.Compared with the model group,myocardial ischemia area in classical ischemia pre-processing group,and middle,high doses of corydalis alkaloid groups all reduced [(44.6±5.7),(46.4±7.2),(45.7±5.7)％ vs(50.4±3.3)％ ](P ＜0.01or P ＜ 0.05).Compared with classical isehemia pre-processing group,there were no significant differences(P ＞0.05) on myocardial ischemia area in the high and middle doses groups except the low dose of corydalis alkaloid group[(48.9±4.4)％ vs(44.6±5.7)％,P＜0.05].②There was no myocardial infarction in sham operation group.Compared with the model group,the infarction size of both classical ischemia pre-processing group and high,middle and low doses levels of corydalis alkaloid groups reduced [(8.9±3.4),(8.5±1.8)(10.1±2.7),(14.2±5.2) ％ vs(50.4±3.3) ％ ](all P ＜ 0.01).Compared with the classical ischemia pre-processing group,there was no significant difference on myocardial infarct size in high and middle doses groups except the low dose of corydalis alkaloid group[(14.2±5.2)％ vs(8.9±3.4)％](P＜0.01).Conclusions There are great similarities between the protection effect of corydalis alkaloid pre-processing and ischemia preconditioning.Corydalis alkaloid may simulate ischemia preconditioning,motivate endogenous protection system and produce the pre-processing effect.