This is a randomized, double-blind, multicentral clinical trial to investigate the efficacy and safety of Recombinant Human TNF Receptor-Ig Fusion Protein for Injection (Qiangke®) in the treatment of Moderate to Severe Plaque Psoriasis. The primary purpose is to assess the different maintaining treatment programme in Moderate to Severe plaque psoriasis by Qiangke®. And the second purpose is to assess the efficacy and safety of Qiangke® in Moderate to Severe Plaque Psoriasis. The trial will include 216 Moderate to Severe plaque psoriasis patients,and at the first stage they will be randomized divided into three group: full-dose of Qiangke® group, half-dose of Qiangke® group and placebo group.And the blind stage will last for 12 weeks. Then at the second stage, all patients will receive 50mg qw of Qiangke® for additional 12 weeks.