Muscle satellite cells play an important role in the growth and development as well as postnatal injury and repair of skeletal muscles, however, it keeps unclear about muscle satellite cell plasticity, effect and mechanism in atrophied muscle. In the present study, we investigated the changes in the satellite cell number and potency of proliferation and differentiation during weightless muscle atrophy induced by mouse hindlimb suspension, and found that the number of quiet satellite cells significantly increased but that of activated cells significantly decreased, and the potential of cell myogenic differentiation also appeared a reduced tendency. Moreover, we verified the above changes of muscle satellite cell plasticity in the cultures of ex vivo single myofibers isolated from weightless atrophied soleus. Finally, Smad3 knockout mice and its wild-type littermates were subjected to hindlimb suspension induced muscle atrophy, and the variability analysis demonstrated that the key role of Smad3 in regulating the plasticity of muscle satellite cells weightless muscle atrophy.