Objective To investigate the infection status of nanobacteria on patients with upper urinary calculi and healthy sub-jects ,and analyze the role of nanobacteria in the formation of upper urinary calculi .Methods The serum ,urine and calculus of 42 patients with upper urinary calculi were investigated by polymerase chain reaction (PCR) and by bacteria cultivation with 10% γ-FBS and PMBI 1640 .The resulting PCR products were sequenced for further comparison with the reported sequence in gene bank . The serum and urine from 30 healthy adults were used as controls .Results After 4 to 6 weeks′culture ,the white or yellow precipi-tate was visible at the bottom of the tube .The positive rate of PCR was 90 .4% in calculous patients urine and 6 .7% in healthy a-dults urine ,as the positive was 92 .8% and 6 .7% in serum .which there is significant difference (P<0 .01) .The positive rate of the nanabactria in urinary calculi was 95 .2% .The coincidence rate was 98 .72% between the PCR products and the reported sequence in gene bank .Conclusion Nanobacteria are widely existed in the serum ,urine and calculus of the patients with upper urinary calcu-li ,this indicate that the nanobacteria might be have the most important influence on the formation process of urinary calculi .