Skeletal muscle mass and function mostly decrease with age in the elderly, and age-related loss of skeletal muscle mass and function is closely associated with increased readmissions and overall mortality. This review summarizes the research on age-related muscle loss and dysfunction, focusing on the measurement of muscle protein synthesis and decomposition, affecting factors and molecular regulatory mechanisms in the process of aging. It is aimed for an understanding of the research on sarcopenia in the elderly and promotion of its further research.