Objective To determine the effects of urate oxidase (Uox) gene knockout ( Uox ^{-/ -} )-induced spontaneous hyperuricemia on the body weight, blood pressure, and blood physiological and biochemical parameters of C57BL/6 J mice. Methods Both female and male C57BL/6 J mice at six- and twelve- week-old were contained, including wild-type ( Uox ^{+/ +} ), urate oxidase knockout heterozygotes ( Uox ^{+/ -} ) and urate oxidase knockout homozygous ( Uox ^{-/ -} ) mice. Mice body weight, blood pressure, and major blood physiological and biochemical parameters were observed. Results The average body weight of the 6-week-old female Uox ^{-/ -} mice and all male Uox ^{-/ -} mice was significantly lower than that of the Uox ^{+/ +} mice ( P < 0. 05). The body weight of the male Uox ^{+/ +} and Uox ^{+/ -} mice was significantly higher than that of the female mice of the same genotype and age ( P < 0. 05), but the body weight showed no statistical differences between the Uox ^{-/ -} mice of different sex. Compared with Uox ^{+/ +} and Uox ^{+/ -} mice of the same age, 6-week-old female Uox ^{-/ -} mice and 12-week-old male Uox ^{-/ -} mice had significantly higher blood pressure ( P < 0. 05). Blood physiological parameters showed that the red blood cell (RBC), hematocrit (HCT), mean corpuscular volume (MCV), and hemoglobin (HGB) of the Uox ^{-/ -} mice were significantly lower than those of the Uox ^{+/ +} mice ( P < 0. 05), and their mean corpuscular hemoglobin concentration (MCHC) and plateletcrit (PCT) were higher than those of the Uox ^{+/ +} mice ( P < 0. 05). Compared with the Uox ^{+/ +} mice, RBC, HCT and HGB of the Uox ^{+/ -} mice were significantly decreased ( P < 0. 05), while PCT was significantly increased ( P < 0. 05). The blood biochemical parameters showed that albumin ( ALB), total bilirubin (TBIL), and direct bilirubin (DBIL) of the Uox ^{-/ -} mice were lower than those of the Uox ^{+/ +} mice ( P < 0. 05), and their uric acid (UA), creatinine (CREA), blood urea nitrogen (BUN), cholesterol (CHOL), and low density lipoprotein (LDL) were significantly higher than those of the Uox ^{+/ +} mice ( P < 0. 05). Conclusions The basic biological data of C57BL/6 J mice with the urate oxidase gene knockout were established. Uox ^{-/ -} -induced spontaneous hyperuricemia could cause abnormal changes in body weight, blood pressure, kidney function, and lipid metabolism of mice.