At present, in the case of backpacks for the youth on the market, weight is mainly designed to be carried by
shoulders, which ignores the role of the waist in load-carrying. Long-term improper loading of backpacks can affect
the growth of one’s spine. In order to balance the load on shoulders, waist, and hip, a weight loss backpack was
designed to change the way of gravity transmission through the hip belt and elastic bar structure. Firstly, the
biomechanical analysis of the state of the human backpack and the spine was carried out, and the weight-reducing
principle of the backpack was achieved according to the force analysis. Then, the torque analysis was carried out on
shoulders, waist, and hip of the weight-reducing backpack, and a design plan was proposed. Next, the traditional
backpack was analyzed by ADAMS. The dynamic simulation of human shoulders, waist, and hip loads was carried out with the weight-reducing backpack under three road conditions of even ground, uphill, and downhill conditions, and
the moments of shoulders, waist, and hip in the cases of the two backpacks were analyzed by MATLAB. The results
show that the weight-reducing backpack could reduce the shoulder moment by 6.1% and the waist by 5.4%; the ratio
of the shoulder moment of the weight-reducing backpack to the combined moment of the waist and hip was 4.17, and
the ratio of the traditional backpack was 6.58. A conclusion could be drawn that the weight-reducing backpack could
reduce the load on shoulders and waist. At the same time, it was found that the smaller the ratio of the shoulder
moment and the combined moment of the waist and hip is, the greater the moment transferred to the hip, and the better
the balance of the backpack, indicating that the weight-reducing backpack outperforms the traditional ones.