This study aimed to evaluate the association between skeletal muscle mass and long-term all-cause mortality among nonagenarians and centenarians in China. We used data from the Project of Longevity and Aging in Dujiangyan (PLAD). A total of 738 community-dwelling people aged ≥ 90 years (mean age of 93.5 ± 3.2 years) were analyzed in this study. The appendicular skeletal muscle mass (ASM) was estimated using a previously validated anthropometric equation. The information on the survival status was requested from the local government registries during the 4 year follow-up period following the baseline investigation. The mean muscle mass index (SMI) was 6.11 ± 0.53 kg/m2 in men and 4.00 ± 0.63 kg/m2 in women, respectively. Low muscle mass was associated with a higher risk of death (hazard ratio [HR] 1.54; (95% confidence interval [CI]:1.10-2.16) in women; however, no significant association was found in men. Disability in activities of daily living (ADL) (HR = 1.73; 95% CI: 1.13-2.63) in men and women and cognitive impairment (HR = 1.49; 95% CI: 1.05-2.13) in men were also associated with increased all-cause mortality. In conclusion, low muscle mass were predictors of long-term mortality in nonagenarian and centenarian women.