One way to calculate net forces utilizes the Newton-Euler equations where the human body is assumed to consist of solid elements. However, previous research only applied them to open-loop motion in which both legs are off the ground or only one leg is on the ground. It has been problematic to analyse closed-loop motions such as walking in which both feet are on the ground. This study suggested a way to calculate net forces throughout a walking cycle. Furthermore, one walking trial of each subject (3 in total) was conducted to validate with the proposed methods. This study showed that the correlations between force plates and calculated GRF were strong, in particular for the z axis, in the left limb ranged from 0.92 to 0.99, in the right limb from 0.99 to 0.98. Thus, the proposed method was considered to successfully calculate the net forces during walking.