Objective To explore the way to reduce the absorption of irrigating fluid during PCNL. Methods The amount of absorbed fluid during PCNL in 20 cases (13 males and 7 females)was monitored by ethanol method. The average age was 40 years old. The maximum diameter of calculi by average was 25 mm. Heart rate and mean arterial pressure were monitored during operation.Haemoglobin concentration, serum Na+, K+, Cl-, carbon dioxide-combining power and serum creatinine were measured before and after operation. The amount of irrigating fluid, the duration of operation, and the intrapelvic pressure were recorded. Results The absorbed volume of irrigating fluid in 20 cases was from 50. 2 to 685.0 ml. There was no significant difference in heart rate, mean arterial pressure, serum Na+ , K+ , Cl- and serum creatinine between pre-operation and post-operation(P>0.05), but the postoperative haemoglobin concentration (130.4±16.3 g/L) and carbon dioxide-combining power (24.1±3.2 mmol/L) were lower than that before operation( 142.6±15.6 g/L,26.4±2.0 mmol/L), the differences were significant (P<0. 05). The mean volume of absorbed irrigating fluid in patients with the cumutative time of the intrapelvic pressure higher than 30 mm Hg >10 min,the duration of operation >1 h, or the amount of irrigating fluid >10000 ml was 381. 1, 301.6,261.6 ml respectively, which was higher than that in the other cases (142.9, 136.4, 130.2 mi), the differences were significant (P<0.05). Conclusions The ethanol method is simple, convinent,safe, valid, and is suitable for patients with compromised cardiorespiratory or renal function, who are more likely to develop volume overload because of fluid absorption.