Abstract: To achieve the green and low-carbon transformation of the ironmaking system, in response to the special thermal behavior issues of Ansteel's self-produced ultra-fine magnetitehematite mixed concentrate, such as extremely fine particle size, poor pelletizing property, strong oxidation heat release, narrow roasting window, and easy overheating and cracking, a systematic study was carried out on the characterization of raw material physical and chemical properties, optimization of pelletizing parameters and ore blending structure, design of the straight-grate system, and evaluation of metallurgical properties, and a complete set of key technologies for the preparation of fluxed pellets was formed. On this basis, the 4 million t/a fluxed pellet production line with the straight-grate system in Donganshan Sintering Plant of Ansteel Group Mining Co.,Ltd. achieved stable operation. The TFe of the fluxed pellets was approximately 64.0%, the SiO₂ was about 3.8%, and the basicity was stable at 1.0. Compressive strength was ≥ 2 800 N per piece, drum strength was >92%, reduction degree was >78%,reduction expansion rate was <12%, low-temperature reduction pulverization rate(RDI_{+3.15 mm})was > 90%. According to the “Guidelines for Accounting and Reporting of Carbon Emissions in the Iron and Steel Industry（for Trial Implementation）”, after the pelletizing process replaced the original 360 m² sintering machine, the carbon emission intensity of the product decreased from 199.02 kgCO₂/t sintered ore to 40.64 kgCO₂/t pelletized ore, representing a 79.58% emission reduction.This study provides an engineering example for the preparation of fluxed pellets from ultra-fine mixed iron concentrate resources and their low-carbon application.