Conventional percutaneous nephrolithotomy (PCNL) is usually performed in a prone position, which compresses the thorax and results in difficulty in rescue during operation. When PCNL is performed in a supine position, the flank renal puncture area is limited, so it is difficult to treat disseminated and complex renal calculi. Herein, we introduce a modified semisupine position for performing PCNL, which has numerous benefits as well as safe and effective. Between May 2002 and May 2009, a total of 452 patients with renal calculi were treated with semisupine PCNL. The patient was placed in 45° semisupine position during the procedure, with the affected flank arched as much as possible. In this series, no one converted to open surgery. The average operating time was (115.2 ± 44.5) min. Single tract PCNL was performed for 80.97% of the cases, two tracts 13.94%, three tracts 4.65%, and four tracts 0.44%. The upper, middle, and lower calix tracts accounted for 12.1, 63.0, and 24.9%, of procedures, respectively. Stone-free rate was 85.7% overall, 92.2% for single calculus (83/90), and 72.9% for staghorn calculi (78/107). Major postoperative complications occurred in 3.3% of the cases. This study demonstrated PCNL in a semisupine position is an effective alternative for treating renal calculi, which combines the advantages of PCNL in a prone position, and PCNL in a supine position. The semisupine position allows easier irrigation of stone fragments, is more comfortable for the patient, and facilitates monitoring of anesthesia.