Objective To investigate the urodynamics of bladder function in patients suffering from benign prostate hyperplasia (BPH) and prostatitis. Methods One hundred and eighty-seven inpatients with BPH hospitalized in our department from June 2009 to June 2012 were recruited in this study. They were assigned to two groups according to being accompanied with prostatitis or not, that is, BPH group (n＝91) and BPH combined with chronic prostatitis (CP) group (BPH/CP group, n＝96). Urodynamic indices, such as maximum bladder capacity, maximum detrusor pressure, bladder stability and maximal urethral closure pressure were measured and then compared between the two groups. Results There was no significant difference in the urodynamic parameters, including maximum bladder capacity (P＝0.741), maximum detrusor pressure (P＝0.872) and maximal urethral closure pressure (P＝0.590) between the two groups. But, simple BPH patients had better bladder stability than the BPH/CP group [(158.0±42.7) vs (79.6±30.0)ml, P＝0.032]. Conclusion BPH combined with CP mainly manifests bladder instability urodynamically, which further leads to urinary frequency, urgency and discomfortableness.