AIM: To investigate the changes of bladder volume , pressures and pelvic nerve firing induce by different speeds and ways of instillation .METHODS:Female SD rats (n=20) were randomly divided into 2 groups.The rats in group A was performed using 3-F polyethylene tubing inserted into the bladder through the urethra .The rats in group B were performed using 3-F tubing inserted into the dome of the bladder and secured by silk suture .The rats in both groups were infused with saline into the bladder at different speeds of 50, 100, 200 and 400μL/min.The changes of bladder vol-ume and pressure were recorded by urodynamic measuring devices .The changes of pelvic nerve firing during instillation were recorded by multi-channel physiologic recorder .RESULTS:In group A, the maximum firing frequency , bladder leak point pressure ( BLPP) and maximum voiding pressure ( MVP) were increased with the increase in the instillation speed . No significant difference of the maximum bladder capacity (MBC) at different speeds was observed .In group B, the maxi-mum firing frequency had no significant difference at different speeds .MBC was decreased with the increase in the instilla-tion speed , and exhibited significant decrease at 200 and 400 μL/min.No significant difference of BLPP and MVP at dif-ferent speeds was observed .Compared with group A , the maximum firing frequency and MBC in group B significantly de-creased at different speeds .However , BLPP and MVP in group B were higher than those in group A at the speeds of 50 and 100 μL/min.CONCLUSION:Different instillation speeds with the method of group A will not change the bladder volume but influence the pelvic nerve firing , so the process of method A may take various speeds according to different aims .How-ever, process of method B at the speed of over 200 μL/min may not be good to MBC, thus instillation under 200 μL/min is re-commended .