With regard to the network design problem of the low-carbon supply chain based on online shopping, the concave function is used to minimize the supply chain operation cost including the carbon emission cost, the logistics cost and the fixed cost of the distribution center. Firstly, the Lagrangian relaxation algorithm is used to decompose the problem into two sub-problems, because the problem can not be solved directly. And the Lagrangian heuristic algorithm is proposed based on the sub-problem solution. Then, the model is analyzed by the simulation application on the supply operation cost and the network design of the supply chain. Finally, the analysis results show that resources allocation of the low carbon supply chain can be optimized if the carbon emission cost is considered during supply chain designing.