The invention provides a fluidized-bed low-rank coal upgrading utilization system and method, and belongs to the technical field of low-rank coal upgrading utilization. According to the invention, a washing system, a pyrolysis system and an iron-making system of the low-rank coal are coupled together. Firstly, the low-rank coal is subjected to washing treatment so that size grading of the coal is completed while waste stone is exhausted. The coal powder different in particle size is used for a coking system to prepare coke and joins in medium and low temperature pyrolysis to prepare semicoke. The semicoke obtained through pyrolysis is used as coal for sintering and blended coal for injection, respectively; the by-product gas of pyrolysis is fed into a hot blast stove for combustion, wherein waste heat generated by the sintering and coking process systems is recovered for the washing system and the pyrolysis system; and finally, the sinter, the hot air, the injection coal and the coke are fed into a blast furnace for iron-making. According to the invention, the separation, grading, drying and pyrolysis of the low-rank coal are realized; the low-rank coal is utilized after being upgraded in stead of partial high-rank coal; and therefore, the cost of iron per ton can be effectively reduced and the stress of the demand of the iron and steel industry for the high-rank coal can be reduced.