The invention relates to the technical field of biological and medical technologies, in particular to a rat infrarenal abdominal aortic aneurysm model constructed through a retroperitoneal approach and a construction method. The operation is relatively simple, risks caused by the abdominal approach can be avoided, pressurized perfusion is not adopted, the perfusion time is shortened to 20 min, lower limb ischemia does not occur, the tumor formation rate is not affected, damage to blood vessels is extremely small, bleeding can be stopped through local compression after perfusion is finished, and the operation success rate is remarkably increased; The construction method comprises the following steps: S1, performing fasting for 12 hours before an operation of a rat, anesthetizing the rat with pentobarbital sodium according to 40-50mg / kg, taking a right side lying position after satisfaction of anesthesia, conventionally preserving skin, performing disinfecting, taking a connecting line from the lower part of a left side posterior axillary line costal margin to the root of a thigh as an incision with the length of 3-3.5 cm, cutting the skin, subcutaneous tissue and muscles layer by layer to see the retroperitoneal fat tissue, finding a potential gap between the peritoneum and lumbar dorsal muscles along the fat tissue, separating the gap by a cotton swab to reach the aorta abdominalis, and separating the aorta abdominalis from the inferior vena cava.