Mesenchymal stem cells (MSCs) are a kind of adult stem cells that can differentiate into bone, cartilage and adipose cells. Adipos-derived Mesenchymal Stem Cells(AD-MSCs) were isolated from fat tissues and were reported to treat moderate to severe psoriasis vulgaris and psoriasis arthritis successfully by case reports. For the mechanism of the disease, involvement of the immune system in psoriasis is now widely accepted. Mesenchymal stem cells (MSCs) are found to have the function of immunomodulation, migration to skin lesions, limitation of autoimmunity. Therefore, investigators supposed that the injection of AD-MSCs could be beneficial for treatment of moderate to severe psoriasis.