The purpose of this study is to investigate the effect of quadruped exercise according to the change of the support surface on the muscle thickness and muscle tone of the multifidus and erector spinae muscles. Thity healthy adults (16 males and 14 females) voluntarily participated in the experiment. The Q (Quadruped) and Q-L (Quadruped-Lifting right leg) exercises were performed on a stable support surface; whereas the Q-LT (Quadruped-Lifting right leg using TOGU dynamic airchusion) and Q-LS (Quadruped-Lifting right leg using Sling) exercises were performed on an unstable support surface. Outcome measurement included muscle thickness and muscle tone measurement using ultrasound equipment and Myoton, respectively. Repeated measures ANOVA was used for data analysis. The result of the study showed that in Q-L, Q-LT, and Q-LS, the muscle thickness of the multifidus and erector spinae was significantly increased compared to Q (p<.05). The muslce tone of the multifidus in Q-LT and Q-LS, increased compared to Q (p<.05). The muscle tone of the erector spinae muscle was significantly increased in Q-L, Q-LT and Q-LS compared to Q (p<.05). The muscle thickness was significantly increased in the unstable support surfaces in Q-LT and Q-LS compared to the stable support surfaces of Q and Q-L (p<.05). However, a significant difference between Q-LT and Q-LS was absent, which were the unstable support surfaces. Therefore, the results of this study showed that the quadruped exercise was more effective on an unstable support surface. This result can be used as useful data for the prescription and application of various exercises in clinical practice.