The utility model relates to an upgrading utilization system for a low rank coal fluidized bed and belongs to the technical field of low rank coal upgrading utilization. According to the upgrading utilization system for the low rank coal fluidized bed, a low rank coal washing system, a thermolysis system and an ironmaking system are coupled together; low rank coal is subjected to washing firstly, recrement is discharged while size grading of coal is completed; coal dusts with different grain diameters are used for preparing coke by virtue of a coking system and participates in low temperature thermolysis for preparing semicoke; semicoke obtained through thermolysis is respectively applicable to coal used for sintering and injection coal blending, thermolysis byproduct coal gas is fed into a hot blast stove as combustion supply, waste heat produced by sintering and coking technological systems is recycled and used by the washing system and the thermolysis system, and finally sintering ore, hot blast, injection coal and coke are fed into a blast furnace for ironmaking. The upgrading utilization system for the low rank coal fluidized bed realizes low rank coal washing, grading, drying and thermolysis, the low rank coal replaces part of high rank coal through upgrading utilization, cost per ton iron can be effectively reduced, and stress of the iron and steel industry on demand of the high rank coal can be alleviated.