[Objective] To investigate the effect of angiogenesis and collagen synthesis in peri-infarct area of the L-Arginine therapy for acute myocardial infarction rats. [Methods] The acute myocardial infarction rats model was established by ligation of the left anterior descending of coronary artery. Thirty male Sprague-Dawley rats were randomly divided into three groups: L-Arginine group, sham group, normal saline group (NS group). Four weeks after ligation, cardiac function, scar area, plasma concentration of BNP, angiogenesis and arteriogenesis, myocardial collagen I and eNOS protein, the mRNA expression of collagen I were studied. Echocardiography, Masson staining, enzyme-linked immunosorbent assay (ELISA), immunehistochemistry, western blot and quantitative polymerase chain (qPCR) reaction were performed. [Results] Four weeks after ligation, compared with the control group, LVEF, LVFS were higher in L-Arginine group, While LVEDD and LVESD decreased (P < 0.01). Average scar percentage and plasma concentration of BNP were lower in L-Arginine group (P < 0.01). The CD31-positive microvessels and α-SMA positive microvessels in peri-infarct area were higher in L-Arginine group (P < 0.01), while collagen I protein and mRNA expression was decreased in this group (P < 0.01). [Conclusions] L-Arginine improves cardiac function and reduces infarction size in AMI rats, the possible mechanism is related to dual function of promoting angiogenesis and arteriogenesis, regulating collagen I expression is also one of the important mechanisms.