Objective To investigate the effect of the Xingpi Yanger granules on bladder urodynamics and bladder external sphincter activity in normal rats. Methods Sixty healthy animals were divided into five groups: a control group; Xingpi Yanger granule 9. 2, 4. 6, and 2. 3 g/ kg groups; and oxybutynin group, with 12 rats in each group. Experimental groups were given the drug by gavage for 7 consecutive days, and the control group was given equal volumes of pure water in the same way. After the last administration, we measured intravesical pressure and external urethral sphincter electromyography under light anesthesia and deep anesthesia when the rats were urinating. Rats’ bladder pathomorphology was observed by hematoxylin-eosin staining. Results Xingpi Yanger granules obviously decreased rat basal bladder pressure ( BBP) under light and deep anesthesia. The high-dose group, especially, showed significantly improved maximum bladder capacity, peak number of P2 phase, and bladder compliance under light anesthesia. There were no significant differences in the structural changes to the bladder in any group. Conclusions Xingpi Yanger granules significantly reduced BBP, increased the maximum bladder capacity and bladder compliance, and vigorously promoted bladder urination. The mechanisms may be related to the relaxation of bladder smooth muscle and improvements in bladder functional status.