Objective: This cross-sectional study is based on the Korean Frailty and Aging Cohort study involved 1,053 people aged 70 years or over. Anthropometric, physical performance, and laboratory data were collected. Dual energy X-ray absorptiometry was conducted for appendicular skeletal muscle mass (ASM). Walking speed and maximal handgrip strength were measured.  Methods: The mean age of the participants was 75.8 years, and 50.7% of them were female. Serum myostatin level in men (3.7±1.2 vs. 3.2±1.1 ng/ml, p<0.001) was higher compared with that in women. Serum myostatin level was associated with appendicular skeletal muscle mass (ASM) index (r=0.285, p<0.001) and eGFR by cystatin C (r= -0.013, p<0.001). While serum myostatin level was associated with handgrip strength in men and walking speed in women, these associations disappeared after adjustment. Serum myostatin/ASM ratio was associated with handgrip strength in women. Results: Higher serum myostatin levels was related with higher muscle mass and better physical performances in elderly. Serum myostatin/ASM ratio may be a predictor for physical performance rather than myostatin. Conclusions: Objective: Higher myostatin has been proposed as a biomarker for sarcopenia. Recent studies show higher myostatin was associated with physical fitness and performance. This study aimed to examine the significance of myostatin in the association between muscle mass and physical performance in the elderly.  Methods: This cross-sectional study is based on the Korean Frailty and Aging Cohort study involved 1,053 people aged 70 years or over. Anthropometric, physical performance, and laboratory data were collected. Dual energy X-ray absorptiometry was conducted for appendicular skeletal muscle mass (ASM). Walking speed and maximal handgrip strength were measured.  Results: The mean age of the participants was 75.8 years, and 50.7% of them were female. Serum myostatin level in men (3.7±1.2 vs. 3.2±1.1 ng/ml, p<0.001) was higher compared with that in women. Serum myostatin level was associated with appendicular skeletal muscle mass (ASM) index (r=0.285, p<0.001) and eGFR by cystatin C (r= -0.013, p<0.001). While serum myostatin level was associated with handgrip strength in men and walking speed in women, these associations disappeared after adjustment. Serum myostatin/ASM ratio was associated with handgrip strength in women. Conclusions: Higher serum myostatin levels was related with higher muscle mass and better physical performances in elderly. Serum myostatin/ASM ratio may be a predictor for physical performance rather than myostatin.