Backpacks have been widely used to increase load carriage capacity, but the pressure at the body surface may cause discomfort or pains.  Previous studies revealed that chest straps and hip belts of backpack helped to relieve the discomfort feeling, but how the pressure changes are still unclear. In this study, the influence of strap tying and the posture change on the pressure distribution were investigated. A daily backpack with 5kg load was used in the experiment. Five young females carried the backpack to stand, walk and jog. The pressures were measured at the shoulder, waist and hip, which are the primary load bearing regions. The trunk forward lean angle (TFL) was captured by using the Vicon motion capture system. Results showed that tying both the chest strap and hip belt reduced the shoulder pressure and increased the pressure at the hip and waist. From standing, walking to running, TFL increased gradually and the pressure transferred from shoulder to back and hip. These findings help us to better understand and quantify the load carrying performance of a backpack.