This is a multicenter, double-blind, randomized, placebo-controlled study designed to evaluate the efficacy and safety of Botulinus Toxin Type A for Injection (HengLi®) in patients with overactive bladder (OAB) . Approximately 216 subjects will be enrolled. Subjects will be randomized 2:1 to receive intradetrusor injection of Botulinus Toxin Type A for Injection (HengLi®) 100 U or placebo. The study contains two parts: core double-blinded phase and extension phase. In the core double-blinded phase, eligible subjects must attend three study visits posttreatment 12 weeks. During the extension phase, subjects must also attend three study visits (12 weeks). The primary efficacy variables is the change from baseline in the daily average frequency of micturition at week 6 after the first treatment.A 3-day paper bladder diary will be used before each study visits (screening period, the second week, the sixth week, the twelfth week, the fourteenth week, the eighteenth week and the twenty fourth week ) to collect all OAB symptoms (episodes of urgency, incontinence, micturition and nocturia) and volume per voidSafety parameters will also be measured, including adverse events, vital signs (pulse and blood pressure) and clinical laboratory tests (haematology, serum chemistry and urinanalysis).