Previous studies have indicated that the gene mutations of absorption distribution metabolism and drug target may affect the efficacy of Methotrexate in vivo.To investigate the influence of genetic factors on the curative effect , to find the relationships between genetic variants and the response of Methotrexate to treatment of Psoriasis Vulgaris.Investigators analyzed the various levels of genetic factors, including: 1.To analysis the key gene variants which associated with ADME(absorption, distribution, metabolism and excretion) affect the efficacy of Methotrexate; 2.Direct full genetic sequencing of MHC genes, to explore the genetic variations of efficacy and side effects; 3. Direct sequencing of all exons in the gene in the patients of the response of serious and effectively, to explores the rare genetic variation may cause deterioration of treatment by Methotrexate.