Objective To analyze the cause of puncturing failure in ultrasonography guided minimal-invasive percutaneous nephrolithotomy (MPCNL). Methods A retrospective analysis involved total 612 patients with upper urinary tract lithialisis treated with MPCNL from May 2005 to May 2010.382 cases were acupunctured by traditional G18 puncturing instrument (group A),and the other 230 cases were performed by the improved ARROW Raulerson blue syringe (group B).The average renal pelvis range was 24 mm vs.21 mm before operation,and largest diameter of renal calculi was 3.7 cm vs.3.8 cm (P ＞ 0.05).Success rate and time cost as well as therapeutic effect were compared between the 2 groups. Results There were 29 cases of puncturing failure in group A (totally 382 cases) while only 2 in group B (totally 230 cases).The successful rate of establishment of working channel was significantly higher in group B (P ＜ 0.05).Average time of puncture procedure was 5.1 min and 4.8 min respectively (P ＞ 0.05).There was no puncturing-related severe complication in any group.The unsuccessful cases in the group A and related causes were:5 cases for obesity,13 cases for puncture needle slipping,9 cases for channel dropout,and 2 cases for needle route dropout.However,only 2 cases failed in group B,the accurate position of calculi was at upper and lower calyx.One case was over-weighted,another was because of pathway-loss during the calculi elimination processs.And the one-off puncture successful rate of A and B group was 92.4％ vs.99.1％,and the one-off puncture successful rate was significantly higher in group B. Conclusions Overobesity of patients is an important cause of puncturing failure for sonographically MPCNL.The establishment of working-channel with ARROW Raulerson blue syringe could be feasible and the success rate was significantly higher.