Abstract: Objective:To evaluate the clinical application of the percutaneous nephrolithotomy(PCNL) guided by B ultrasound in the treatment of calculous pyonephrosis under local anesthesia.Methods:Thirty-seven cases with calculous pyonephrosis were treated with phase Ⅰ renal biopsy to drain pus guided by B ultrasound under local anesthesia,then the patients were treated with phase Ⅱ standard channel percutaneous nephrolithotomy when the general conditions of patients were improved.Results:Thirty-seven cases were successfully punctured and removed the obstruction,the ipsilateral renal function in 30 cases and 7 cases recovered to normal and improved,respectively.The operation time of phase Ⅱ standard channel percutaneous nephrolithotomy was 25 to 84 min.No residual stones,systemic inflammatory response syndrome and severe bleeding in all cases were found,and the hospitalization time was 10 to 21 d.Conclusions:Phase Ⅰ renal biopsy drainage of pus and removing urinary tract obstruction can improve the security of the phase 2 PCNL,which has an important significance in treating calculus pyonephrosis.