Abstract: Against the background of the low-carbon transformation of the iron and steel industry and the national dual-carbon goals, exploring low-carbon and clean alternative fuels and reducing carbon emissions from blast furnace ironmaking have become important research topics in the metallurgical field. As a typical carbon-neutral and renewable fuel, biomass exhibits excellent emission reduction benefits in blast furnace injection and acts as a vital technical route for the development of low-carbon metallurgy in the steel industry. However, biomass has the problems of high alkali metal content, poor grindability and low energy density. Combined with imperfect pretreatment processes and poor economic efficiency, the above problems severely limit its large-scale industrial application in blast furnace injection. This paper took biomass for blast furnace injection as the research object, systematically analyzed the core practical challenges and internal action mechanism of biomass injection. It clarified that alkali metals including potassium and sodium in biomass tended to undergo gasification migration and enrichment circulation in the high-temperature blast furnace system, which further destroyed the microstructure of coke and aggravated the deterioration of coke metallurgical properties. Meanwhile, this paper indicated that the dense three-dimensional network structure formed by biomass components was the key cause of its poor grindability. Aiming at the above technical bottlenecks, this paper systematically summarized the process characteristics and application limitations of multiple upgrading methods including ultrasonic cavitation dealkalization, baking pretreatment, steam explosion and hydrothermal carbonization. A novel collaborative treatment technology of dealkalization and grinding aid was proposed. Depending on green and recyclable additives, the technology realized the deep removal of alkali metals and synchronous improvement of grindability in a single step. Experimental results show that the proposed technology can control the total alkali metal content of biomass within the standard range for blast furnace injection and significantly optimize particle size indicators, and has obvious cost advantages compared with traditional processes. The research confirms that single technical optimization or multi-process coupling can make various performance indicators of biomass meet the technical requirements of blast furnace injection. The processed biomass has great application potential for large-scale pulverized coal substitution and can provide effective support for the application of biomass in blast furnaces.