A rats feedig trial was conducted to investigate the effects of phosphorus levels on phosphorus uptake to reveal the mechanism of phosphate (Pi) uptake. One hundred and twenty male Kunming rats with body weight of 18 to 22 g were randomly divided into 4 treatments, and each treatment consisted of 5 replicates with 6 rats per replicate. The 4 treatments were fed the basal diets supplemented with 0.2%, 0.4%, 0.6% and 0.8% total phosphate. The experiment lasted for 14 days. Calcium (Ca) and Pi concentration in bone and serum and Na+/PiⅡb mRNA expression were determined. It showed that Na+/PiⅡb mRNA expression was 3.10 （P＜0.01), 3.07 （P＜0.01) and 2.17 （P＜0.05) folds as that of normal Pi treatment in ileum, jejunum and duodenum, respectively, but 9.19 （P＜0.01), 12.86 (P＜0.01) and 23.15 (P＜0.01) folds in kidney lower than that of other three treatments. Na+/PiⅡb mRNA expression was the highest in ileum, and that of 0.2% Pi treatment was 1.34 (P＞0.05), 3.43 (P＜0.05） and 95.53 （P＜0.01) folds as in jejunum, duodenum and kidney, respectively. Na+/PiⅡb mRNA expression of 0.2% Pi treatment was the lowest in renal, which was 70.92 (P＜0.01) and 27.85 (P＜0.01) folds lower than that in jejunum and duodenum, respectively. Pi uptake of 0.2% Pi treatment was 22.11% and 19.35% higher than that of 0.6% Pi and 0.8% Pi treatments (P＜0.05), respectively, and VD3 content in serum was significantly higher than that in the other three treatments （P＜0.05). The results indicate that Na+/PiⅡb mRNA expression and Pi uptake in ileum and jejunum are significantly increased by low Pi, while those in renal are decreased. The expression of Na+/PiⅡb mRNA is the highest in ileum, and the lowest in renal under low phosphate.［Chinese Journal of Animal Nutrition, 2010，22（4）:1000-1006］