Abstract： Objective To investigate the therapeutic effect of phloroglucinol Injection to prevent unstable bladder on post-prostatectomy. Methods Ninty-five cases of patient intravenous infusion of phloroglucinol Injection on suprapubic prostatectomy for painkiller, in the same term, 66 cases intramuscular fix (dose) quantify analgesia [ dolantin 75mg + anisodamine (654-2) 10 mg] for the control group. Results Two cases of the group A appear unstable bladder within 72 hours, bladder perfusion fluid become clear is rang 12-24 hours;average 20 hours;18 cases of the group B appear unstable bladder, bladder perfusion fluid become clear is rang 36 ～ 72 hours average 52 hours ;compare between the two groups there is an significantly difference ( P ＜ 0.05 ) ;Conclusion Intravenous infusion of phloroglucinol Injection may effectively prevent and therapeutic unstable bladder on post-prostatectomy,can be used as normal.