Objective： To investigate the effect of Miniao Paishi Mixture of our hospital on the formation of calcium oxalate renal calculi in rats， and explore its mechanism preliminarily.,Methods,2,Forty healthy male SD rats of SPF grade were randomly divided into normal group， model group， positive control group （potassium citrate） and Miniao Paishi Mixture group， 10 in each group. To establish calcium oxalate kidney stone model in rats， 1% ethylene glycol was given with drinking water， and 2% ammonium chloride was given by gavage. And each group was given corresponding drugs intervention. The 24 h urine volume， urinary oxalic acid content， urinary Ca,2+,， P,3+,， Mg,2+, levels and serum BUN， Cr， Ca,2+,， P,3+,， Mg,2+, levels of rats in each group were observed. Calcium oxalate crystal deposition and pathological changes in renal tissue sections were observed under microscope.,Results,2,①The 24 h urine volume and blood biochemical indexes： the 24 h urine volume of Miniao Paishi Mixture group and positive control group was higher than that of normal group and model group （,P,<,0.05）. Compared with the model group， the levels of 24 h urinary oxalic acid， Ca,2+, and P,3+, in the blood and urine in the Miniao Paishi Mixture group and the positive control group were significantly lower （,P,<,0.05）. Moreover， those in the Miniao Paishi Mixture group was lower than the positive control group （,P,<,0.05）. ②Comparison of serum and urinary Mg,2+, levels： the positive control group and Miniao Paishi Mixture group were higher than model group （,P,<,0.05）. There was no significant difference in Mg,2+, level in blood and urine between positive control group and Miniao Paishi Mixture group （,P,>,0.05）. ③Renal function： the Miniao Paishi Mixture group and positive control group were significantly better than the model group （,P,<,0.05）. ④Pathological change： compared with the model group， the deposition area of calcium oxalate crystals in the renal tissue was significantly reduced and the renal tubular edema decreased in the Miniao Paishi Mixture group and the positive control group.,Conclusion,2,Miniao Paishi Mixture can promote the excretion of oxalic acid， decrease the levels of calcium and phosphorus in blood and urine， increase the level of magnesium in blood， thus inhibit the formation of renal calcium oxalate crystal in experimental rats， and finally play a role in protecting renal function.