During pregnancy, a woman changes especially in body weight, body shape, and endocrine system. Those changes make the pregnant women different from the non-pregnant women in posture and gait pattern. At the same time, activities of daily living become more difficult. But there was still no published paper discussing the posture and gait changes of the pregnant women in details and in a whole. In this study, we used the optimization method to define the hip joint center of the pregnant women. the optimization method can compensate the lack of the anthropometric data of the pregnant women. But the problem of mass distribution in the pregnant women is still necessary to be solved by non-invasive methods, e,g. surface laser scan. Due to the variations of physiological changes in the pregnant women, it was difficulty to standardize the gait analysis of pregnant women, even in the same gestational age. The data of gait analysis were also compared with questionnaires for further analysis. The results revealed that there really was some correlation between the significant finding of gait analysis and sacroiliac pain of the pregnant women. The low back pain often occurred in the following conditions of gait analysis:(1) when the hip extension moment increased; (2) when the knee extension moment decreased; and (3) when the angle of ankle plantar-flexion moment decreased. The gait analysis of the pregnant is a feasible, but complicated method for study.