In this article,we investigate the optimization and coordination of the low-carbon supply chain considering triple bottom line under carbon tax policy.First,we examine the decisions of centralized supply chain considering the triple bottom line.Second,we consider four decentralized supply chain models under wholesale price contract,i.e.,Model Ⅰ,Model Ⅱ,Model Ⅲ,and Model Ⅳ.Then we study the four models under two-part tariff contracts,i.e.,Model Ⅰ-LTT,Model Ⅱ-LTT,Model Ⅲ-LTT,and Model Ⅳ-LTT.The results show that the two-part tariff contracts can perfectly coordinate the low-carbon supply chain in Model Ⅰ-LTT and Model Ⅲ-LTT,while realize Pareto improvement of the low-carbon supply chain in Model Ⅱ-LTT and Model Ⅳ-LTT.Finally,numerical analysis is conducted to assess the impact of carbon tax and Carbon Emission Reduction (CER) investment coefficient on total profit of supply chain before and after coordination.This study provides reliable theoretical basis for low-carbon enterprises in selecting appropriate CER strategies and contracts.