Objective To reveal the rule of the biomechanical remodeling of the aorta by studying zero?stress state of abdominal aorta in strepozotocin-induced diabetic and spontaneously hypertensive rats. Methods The animal model of diabetes with and without hypertension were made on SHR (SHRDM group) and SD (SDDM group) rats respectively by injection of streptozotocin. The opening angle (OA) of their abdominal aorta (AA) was studied by microscope and compare image analysis system.Results (1) OA of AA in SD group became bigger from 1st week to 4th week, and then turned smaller, after 8th weeks became stable. (2) OA in SDDM group increased rapidly from 1st week to 4th week, decreased greatly within 4th to 8th weeks, and increased rapidly again after 16th weeks. OA in SDDM group was smaller at 8th or 16th week (P<0.05) and bigger at 4th or 24th week (P<0.01) than that in SD group. (3) The tendency of OA in SHR group turned out contrary to that in SDDM group , which was bigger than that in SD group at 1st, 8th, 16th week (P<0.01) and smaller at 4th weeks (P<0.01). (4) The change of OA in SHRDM group was similar to that in SDDM group, but smaller at 4th week ( P<0.01 ) and bigger at 8th or 16th week (P<0.05) than SDDM group. Conclusions The zero-stress state of abdominal aorta was abnormal in diabetic and hypertensive rats. The contrary tendency of OA between diabetic and hypertensive groups at early stage suggests that there exsits un-uniform growth obviously in big artery wall of diabetes and hypertension, but the patterns are different.