With the proposal of China's carbon peak in 2030 and carbon neutralization target in 2060，it has become a necessary constraint for power generation industries to continuously reduce greenhouse gas emissions while developing energy. Biomass co-firing technology can reduce CO2 emissions effectively and increase the share of green energy. However，the practical application of co-firing in China's existing coal-fired power plants is still little. Under the current background，economy is the main problem restricting the development of biomass co-firing in China. With the withdrawal of government subsidy，the application of this technology to power generation is facing great challenges. But the carbon tax trading may bring a new turn for the economy of biomass co-firing. In this case，a technical and economic model of power generation with biomass co-combustion was established，the technical potential of replacing coal installed capacity by co-combustion technology was evaluated，and the economic feasibility of biomass co-combustion was studied under the background of carbon tax trading considering different constraints. The results show that the cost balance of biomass co-combustion can be achieved when the standard coal price is 780 yuan/t，carbon tax is 60 yuan/t and biomass price is 450 yuan/t. The sensitivity analysis of parameters shows that under the given heat value，the impact of standard coal price increase of 100 yuan/t is basically the same as biomass price decrease of 50 yuan/t or carbon tax increase of 36 yuan/t on additional cost. The heating value based biomass price，standard coal price and carbon tax all have important influence on the economic feasibility. The lower heating value based biomass price and the higher carbon tax ratio are conducive for the coal price to achieve the profit and loss balance point of co-combustion and pure coal combustion. Because the price of biomass per unit calorific value，coal price，transportation cost and other factors have a positive impact on the economy of co-firing，the economy of co-firing must be determined based on the specific parameters of each power plant.