Objective Methods Weights data of brain，spleen，heart，lungs，liver，kidneys，adrenal glands，testis and ovaries from control group SD rats with 13 weeks，26 weeks，52 weeks，78 weeks and 104 weeks ages was obtained． These weights data and their coefficients were analyzed． Results Weights of brain，spleen，heart，lungs，liver，kidneys，adrenal glands and ovaries were increased in female rats from 13 to 104 weeks． Weights of brain，spleen，heart，lungs，liver and kidneys of male rats were higher than that of female rats，whereas adrenal weights，its organ weight / body weight ratio and organ weight / body weight ratio were significantly higher than that of males from 13 to 104 weeks． Conclusions This study firstly established different week ～ old SD rats organ weight background data and their reference range which in line with experimental animal status in our country and summarized their changes trend．