In recent years,global warming and greenhouse effect have received increasing attention.Countries have also put forward corresponding regulations and policies to curb carbon emissions.Carbon tax,as one of the important policy tools for controlling carbon emissions,is widely adopted by many countries and local governments.Meanwhile,the environmental awareness of consumers is also increasing.Therefore,the optimal carbon tax policy is formulated based on the government’s goal of maximizing social welfare,and the pricing decisions of companies under the carbon tax and increasingly rising consumer environmental awareness,which is of great practical significance for enterprises and policy makers.Due to the fact that the manufacturers are in the complete monopoly situation is relatively rare,they are generally faced with fierce competition in the market,such as electronic and electrical industry.Thus,this research will be conducted in the situation with two competing manufacturers.Specifically,a two-level supply chain consisting of two manufacturers and one retailer is taken as the research object and a three-stage Stackelberg game model with government participation is built.The Stackelberg game model consists of three stages.First,the government decides the carbon tax rate;then the manufacturers decide the wholesale price of their own products;finally the retailer decides the selling price of each product.The problem is solved by the backward induction.The study results show that:(1)when the carbon tax policy is imposed,the wholesale and retail prices of both ordinary product and low-carbon product will rise,and the rising trend of price in ordinary product is more obvious than that in low-carbon product.Compared with the scenario with no carbon tax policy,in the scenario with carbon tax,low-carbon manufacturer has a comparative advantage over ordinary manufacturer in product demand and profit changes.(2)Competition between manufacturers is conducive to carbon tax policy to guide manufacturers to reduce carbon emissions per unit of product and achieve green transformation.In the industry with competing manufacturers,it’s beneficial for both low-carbon manufacturer and ordinary manufacturer to reduce their respective carbon emissions per unit of product.(3)When the competition between manufacturers is not intensive,the implementation of optimal carbon tax policy can significantly improve social welfare;especially when the consumer environmental awareness is low,the implementation of optimal carbon tax policy is more necessary.(4)When the competitiveness between manufacturers is large,the intuitive tax rate of 1 can be regarded as an approximate optimal carbon tax policy to improve the social welfare,regardless of the consumer environmental awareness.In this paper,the issues about the formulation of government’s carbon tax policy and the adjustment of the firms’ operational decisions in scenario with competing manufacturers are answered.Further,the relevant research is enriched under the conditions with manufacturers’ competition,which can provide a basic research framework and idea for low-carbon supply chain that considers upstream competition.