There are conflicting reports as to the association between serum level of magnesium (Mg) and postmenopausal osteoporosis (OP). The purpose of the present study is to clarify the association between serum level of Mg and postmenopausal OP using a meta-analysis approach. We searched articles indexed in Pubmed and the Chinese Journal Full-text Database (CJFD) published as of October 2013 that met our predefined criteria. Seven eligible studies involving 1,349 postmenopausal women from 12 case-control study arms were identified. Overall, pooled analysis indicated that postmenopausal osteoporotic women had a lower serum level of Mg than the healthy controls (standardized mean difference [SMD]=-0.55, 95 % confidence interval [CI]=-0.83 to -0.26). Further subgroup analysis found a similar pattern in Turkey (SMD=-0.66, 95% CI=-0.99 to -0.32) and Belgium (SMD=-0.98, 95% CI=-1.91 to -0.05), but not in China (SMD=0.02, 95% CI=-0.21 to 0.26). And the difference of serum level of Mg between postmenopausal osteoporotic women and healthy controls below the age of 60 years (SMD=-0.61, 95% CI=-1.09 to -0.13) was similar to that among the population over 60 years (SMD=-0.49, 95% CI=-0.80 to -0.18).In conclusion, this meta-analysis suggests that the low serum level of Mg seems to be a risk factor for OP among the postmenopausal women. However, the subgroup analysis found that there was contradiction regarding races and geography, like China and Turkey. Thus, this finding needs further confirmation by trans-regional multicenter study to obtain better understanding of causal relationships between serum Mg and postmenopausal OP.