Reducing unnecessary energy consumption for networks attracts attention worldwide because of its potential economic benefits and environmental impact. Optimizing link weight is a useful and practical way to yield idler network devices that can produce opportunities for power saving. In this paper, we focus on designing link weight for green IP network with minimal energy consumption. We formulate the problem as a Mixed Integer Linear Programming (MILP) which is to minimize the whole power consumption by closing links and line-cards as many as possible based on link weight while satisfying certain network performances. Because the problem is NP-hard, we propose an efficient heuristics, called Static Weight Design Algorithm based on line-card (SWDA (line-card)), which sequentially determines the on/off state of links and line-cards based on rules to solve the problem in approximation way with low complexity. In addition, the link on/off state is essentially determined by link weight assignment. Simulation results reveal that the power savings of SWDA (line-card) can be significant and be close to that of MILP. Moreover, it will be more effective for networks with high node degrees and low traffic load.