In order to estimate the suitable initial height of unloading and to evaluate the injury levels of the general workers' lumbar spine while unloading from different heights, this study utilize the MotionMonitor(superscript TM) system to analyze the force on the lumbar spine in various operation conditions. The experiment elements, including carrying weights (5 and 15 kg) and initial heights of unloading (75, 95, 115, 135, and 155 cm), provide a matrix of total 10 different combinations of operations. The results show that we could avoid causing injuries to muscles and bones from reducing handling weights or decreasing bending angle of the waist. Our study suggests that an ideal workplace design should reduce bending angle of the waist while unloading.