Study aim: Investigation of the validity of the BESTest with Tinetti test, and laboratory tests of force plate and motion camera and evaluation the effect of mental practice on the balance and walking in patients with MS. Design: A double-blind, randomized clinical trial with community-based and pragmatic control group and parallel group design Settings and conduct: Twenty-two MS patients are randomly assigned into two experimental and control groups after completing the consent form and gathering data. All patients in both groups are evaluated in 3 stages.1) The before the intervention, 2)after the intervention, 3) two weeks after the last intervention session. Everyone receives common practice for 3 sessions per week for 6 weeks. Also, the interventions group receives mental practice for 20 minutes in addition to the usual exercises. The method of the second phase (evaluation the validity of BESTest): 17 MS patients and 17 healthy people will be evaluated using Tinetti test, BESTest, force plate (static Balance) and motion camera (Dynamic Balance). Participants/Inclusion and exclusion criteria: Inclusion criterion: MS diagnosis by specialist physician; EDSS = 1-5; People aged 18-18; Satisfaction to participate in the research. ٍExclusion criteria: Pregnancy; mental problems; fractures, presence of implants in the body, a history of attack and recurrence within the last 2 months. Intervention groups: Intervention group includes 11 MS patients who receive 20 minutes of mental training in addition to common practice. Control group includes 11 MS patients who receive the only common practice of occupational therapy. Main outcome variables: Walking; Independence in activity of daily living ; balance.