Objective To investigate the effect of aging on mechanical work patterns of lower extremity joints in older adults during stair descent, so as to enrich the fall-prevention theory of stair walking. Methods Vicon infrared motion capture system and Kistler platform were synchronized to collect the kinematic and kinetic data. The mechanical work was quantified by using parameters such as joint angle, moment, power, and mechanical work contribution of lower joints. Results Older adults demonstrated a consistent trend in joint angle, moment and power of lower limbs with young adults during stair descent. Compared with young adults, older adults showed decreased peak hip flexion moment, the first peak and second peak of knee extension moment, the first peak of ankle plantarflexion moment, the first and second peak peak of knee negative power, peak ankle negative power, net mechanical work of hip, knee, and ankle joints (P<0. 05). Significantl increase was found in peak hip extension moment, peak hip negative s power, and the mechanical work contribution of ankle joint among older adults (P< 0. 05). There was no significant difference in mechanical work of hip and knee joints between two groups (P> 0. 05). Conclusions The mechanical characteristics of lower extremity joints in older adults were significantly reduced during stair descent. Older adults adopted a strategy in mechanical work which was different from young adults. They would increase hip extension to resist the excessive trunk leaning forward, together with the mechanical work of ankle joint as the compensatory mode, so as to improve body stability during stair decent. It is suggested that older adults should mainly increa