Objective To explore the transformation mechanism and changing law of foot arch function in support phase during walking through the analysis of gait parameters and foot arch mechanical structures. Methods Gait parameters, transverse and longitudinal arch angles of 8 subjects at different walking speeds were collected synchronously by motion capture system and plantar pressure test system. One-way repeated measure anova was used to test differences in characteristic values of foot transverse and longitudinal arch angles as well as plantar forces at different speeds. Results In support phase, two eigenvalues appeared in curve of longitudinal arch angle, transverse arch angle and plantar force, and the eigenvalues of three curves were consistent at four types of walking speeds. During walking at 1. 4 and 1. 2 times of the optimum speed, the time of push-off stage was significantly longer than that at 0. 8 times of the optimal speed (P<0. 05). The inflection point and the first peak of the transverse arch appeared earlier than those at 0. 8 times of the optimal speed ( P < 0. 05). The minimum transverse arch angle at 1. 4 times of the optimal speed was significantly larger than that at 0. 8 times of the optimal speed ( P < 0. 05 ), while the time when the minimum angle appeared was significantly earlier (P<0. 05). During walking at 1. 2 times of the optimal speed, the position for the second peak of the longitudinal arch appeared earlier than that at the optimal speed (P< 0. 05). Conclusions In support phase during walking, foot function transformation was realized by both the longitudinal arch and transverse arch. The longitudinal and transverse arch of the foot were lowered to complete buffer function, and the longitudinal arch of the foot was lowered while the transverse arch was raised to increase foot stiffness to complete the push-off function. The faster pace would increase time proportion of the push-off stage in support phase, while the change of the transverse arch and longitudinal arch was advanced. Exploring the change of foot arch and the mechanism of foot function transformation has important guiding significance for understanding the law of foot movement as well as ankle rehabilitation.