A study focused on the 3D gait analysis for the multiple sclerosis patients is designed. A 3D motion capture system is used to track the changes in gait performance involving the selected parameters before and after the treatment, and some changes of multiple gait parameters are successfully found. These changes reflect the subtle functional changes of the patients, and it is also found that the subtle functional changes are closely related to the treatment time. The quantities evaluation based on the gait data is able to compensate the disadvantages caused by the currently widely used evaluations. These objective assessments will assist the clinicians with making more effective treatment decisions and with facilitating new treatment development.