Objective To study the effects of low-dose histamine and serotonin on bladder function of overactive bladder (OAB) rats. Methods OAB model of female SD rat was successfully established by partial bladder outlet obstruction (PBOO) to simulate clinical OAB urodynamic changes. Forty OAB rats were randomly divided into four groups: PBOO+histamine group (2 μg histamine), PBOO+serotonin group (1.1 μg serotonin), PBOO+combination group (combined treatment of 2 μg histamine and 1.1 μg serotonin) and PBOO+normal saline (NS) group. Ten SD rats undergoing sham PBOO and receiving normal saline served as sham group. All subcutaneous injections began at 10 days after PBOO surgery (twice daily for one week). The urodynamic indexes of rats were recorded under conscious state by bladder pressure measurement during urinary storage and micturition, and then bladder tissues were collected, weighted and stained with Masson's trichrome for histological assessment. The quantitative data of groups were compared and analyzed using one-way ANOVA followed by a Tukey's post hoc test. Results Compared with sham group, the other four groups had significantly increased frequency and amplitude of non-voiding contraction, maximum bladder capacity, interval of micturition contraction, residual urine volume and bladder weight (P<0.05). Compared with PBOO+NS group, the amplitude of micturition contraction was significantly increased, the frequency of non-voiding contraction and residual urine volume were significantly reduced in PBOO+combination group (P<0.05). Moreover, histological analysis showed that detrusor arrangement was continuous and close in PBOO+combination and PBOO+histamine groups. Conclusion Combined use of low-dose histamine and serotonin can improve the stability of bladder function during urinary storage and increase the empty efficiency of bladder, which may provide a new way for clinical treatment of OAB.