The aim of this study is to assess effectiveness of α-L-Guluronic acid in patients with multiple sclerosis. In this phase 2, randomized controlled trial, 50patients with multiple sclerosis have been selected who were injecting different forms ineterferon, beta (interferon beta, 1a and interferon beta, 1b) at least 6 months before the trial. Also, the patients have been chosen among active patients on the basis of disease activity who have had at least one relapsing period during 6month or have active lesions in their MRI imaging. ّFrom these patients, 50 patients will be randomly assigned to beta, α-L-Guluronic acid treatment group and will take beta, α-L-Guluronic acid 1000 mg/day for 24 weeks (two 500 mg tablets/day), besides interferon beta. Moreover, 25 patients will be assigned randomly to control group and will take different injecting forms of ineterferon, beta (interferon beta, 1a and interferon beta, 1b) . Additionally, patients do not have other concomitant diseases (hepatic, renal and cardiovascular) or malignancies. Written informed consent will be obtained.The method of blinding in this study is so neither patients participated in the study nor the persons who perform the test will aware of the intervention. In order to allocate the patients randomly into two groups of treatment and control, at first 5 blocks of 10 with C and T letters (The letters indicate the intervention and control groups) are created in each 5patients are belonged to the intervention group and 5 patients are belonged to the control group). Then the blocks are randomly selected and arranged to obtain a sequential combination of 50 letters. Each letter will be placed in a sealed packet according to the obtained sequence. The study is a single center trial and will be performed on the patients of emam hosein, Tehran. Medical history, physical examination and disease activity on MRI imaging will be evaluated by a neurologist before the intervention and 24 weeks after it.