Sit-to-walk (STW) motion is one of the most common action in daily life. Falls frequently occur, when there is impaired ability to perform STW movements. In this study, the relationships between dynamical characteristics of STW motion and physical functions of elderly people were investigated. The experiments were conducted in Malianwa community, one of the highest proportion of the elderly population of Beijing. 128 elderly (51 males and 77 females, above 65 years) participated in this experiment. Participants were classified into four groups (normal, mild, moderate and severe group) based on physical function test and were instructed to perform STW motion at comfortable state. The data of ground reaction force (GRF) and moment (GRM) between left and right foot was recorded, and quantified by sample entropy. The results showed that there were statistical differences among sample entropies of GRF or GRM between left and right foot. In addition, a subset of variables was significant difference among four groups. Statistical difference was found for the following variables: sample entropies of medial-lateral, anterior-posterior, and superior-inferior GRF of left foot during walking (LFx, P＝0.049; LFy, P＝0.025; LFz, P＝0.036, respectively); sample entropies of anterior-posterior, and superior-inferior GRF of right foot during walking (RFy, P＝0.043; RFz, P＝0.006, respectively); sample entropies of medial-lateral GRM of right foot during walking (RMx, P＝0.041). Therefore, the data of GRF and GRM between left and right foot should be acquired and analyzed separately.