This study aims to compare the disease burden of low bone mineral density (LBMD) between China and global populations from 1990 to 2021 and quantify the associations of sex, age, and socio-demographic index with disability-adjusted life years (DALYs). A secondary analysis of LBMD was conducted using comprehensive data from the Global Burden of Disease Study 2021. The absolute number of DALYs and DALYs rates were determined for 1990 and 2021. Joinpoint regression analysis was employed to assess trends in the age-standardized DALYs rate from 1990 to 2021 and over the most recent decade (2012–2021), using the average annual percentage change. Additionally, China’s future trends over the next 20 years were projected based on this analysis. In 2021, LBMD accounted for 17.31 million global DALYs and 3.47 million (95% UI: 2.78–4.24) in China. Despite a decline in China’s age-standardized rate (from 195 to 175 per 1,00,000; average annual percentage change = −0.29%; 95% CI: −0.32 to −0.25), the absolute DALYs more than doubled. The most pronounced increase occurred in adults aged ≥80 years, with older women exhibiting rates 22.5% higher than men. Projections indicate a rise in China’s rate from 175 to 210 per 1,00,000 by 2050, starting in approximately 2040. Women, older adults, and populations in low-middle and middle socio-demographic index regions are high-risk groups that require prioritized attention. These findings highlight the need for age-stratified screening protocols and context-specific resource allocation in low-middle SDI regions.