This study compares the efficacy and safety of generic zoledronic acid (Yigu®) and original zoledronic acid (Aclasta®) in the treatment of postmenopausal osteoporotic women in China. Four hundred and sixty-six subjects will be randomised (1:1ratio) to either Yigu® 5mg IV or Aclasta® 5mg IV treatment arms.

A single infusion of intravenous zoledronic acid decreases bone turnover and improves bone density at 12 months in postmenopausal women with osteoporosis, and it significantly reduced the risk of vertebral fractures additionally.

In this research, the efficacy and safety of generic zoledronic acid injection in the treatment of postmenopausal osteoporosis will be evaluated, using original drug as control drug. It will provide evidence for reasonable clinical administrations.

Inclusion Criteria:

• Postmenopausal women between the ages of 46 and 80（cessation of menses for 12 months for any reason）
• Subjects with osteoporosis diagnosed according to the World Health Organization (WHO) criteria：they had a BMD T-score of -2.5 or less at the spine or femoral neck；or they had low bone mass，defined as BMD T-score less than -1.0 and more than -2.5 at the spine or femoral neck，with the history of fragility fracture(Fracture site included vertebra, hip,proximal humera, distal radius, distal ulna)
• Subjects signed informed consent voluntarily

Exclusion Criteria:

• Any non-primary osteoporosis skeletal disease
• Subjects with abnormal hepatic function and renal function（alanine transaminase(ALT) and aspartate transaminase(AST) are 2 times higher than the upper limits of normal(ULN);plasma creatinine concentration and blood urea nitrogen are more than 1.5 ULN or calculated creatinine clearance less than 60 ml/min）
• Subjects with serum calcium greater than 2.75 mmol/L (11.0 mg/dL) or less than 2.00 mmol/L (8.0 mg/dL)
• Subjects with severe heart disease, blood disease, mental diseases
• Subjects with cancer and other serious progressive disease
• Prior therapy with bisphosphonates within 12 months before trial entry, prior therapy with parathyroid hormone 1-34 or 1-84, estrogen, selective estrogen receptor modulators, strontium more than 2 weeks within 6 months, prior therapy with oral or intravenous glucocorticoid more than 3 months within 6 months
• Subject is hypersensitivity to experimental drugs, comparator drugs and their metabolites
• Subjects who participated in other drugs or medical devices clinical studies as subjects within 3 months before this study
• Subjects judged unfit for this study by investigators