Denosumab is a fully human monoclonal IgG2 antibody to RANKL that being investigated as a therapeutic agent in all bone diseases characterized by excessive bone resorption, such as primary and secondary osteoporosis, metastatic bone diseases, and other diseases involving bone loss associated with increases in osteoclast function. This will be a single-blind, placebo-controlled single-dose study. All subjects will be randomized to denosuamb 60 mg, denosumab 120 mg or placebo in a ration of 3:3:2. The purpose of this study is to evaluate the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of denosumab administered subcutaneously to healthy adults in China. The primary endpoints for safety are: subject incidence of treatment-emergent adverse events, including clinically significant changes in physical examinations, laboratory safety tests, ECG and vital signs. The secondary endpoints are PK and PD (s-CTX1) parameter estimates.