Abstract: The stability of production indexes and technological process of surface ultra-low-grade hematite in Yanshan Iron Mine concentrator is poor due to fluctuation of ore properties. A series of technological optimizations were conducted based on the technological process investigation and industrial tests， in order to improve the system stability and achieve the energy saving， quality-enhancing， cost-decreasing and benefit increasing. ①The dust-setting nozzle diameter of the coarse-fine classifying cyclone increased by 10 mm， optimizing the yield ratio of overflow and underflow from 35%:65% to 20%:80%. ②In the case of replacing the low-chromium steel ball of the first-stage grinding system with the high-chromium steel ball， changing the [?]120 mm+[?]100 mm steel ball to [?]100 mm+[?]80 mm+[?]60 mm steel ball(the gradation ratio is 2∶4∶2)， and reducing the diameter of the dust-setting nozzle by 10 mm， no broken or deformed small steel balls were appeared in the ball mill and underflow-returning ratio was reduced from 450% to 250%~300%. In addition， the ball mill processing capacity increased by about 70 t/h. ③When the feeding slurry pump of second-stage cyclone was replaced by the type of 250ZJ-I-A65 instead of 200ZJ-I-A65， the supporting motor power increased by 65 kW and ball-containing of the second-stage ball mill increased by 4 percentage points， the open numbers of cyclone group adjusted from 5 to 4. On the condition that the pressure of the cyclone feeding increased by 20 kPa and the concentration of feeding decreased by 9.99 percentage points， the classification efficiency of the cyclone increased by 19.14 percentage points and the concentration of the second-stage grinding increased significantly by 3.74 percentage points. The content of -0.074 mm in discharge increased significantly by 5.40 percentage points when the content of -0.074 mm of feeding decreased by 3.80 percentage points. ④The separation effect of spiral chute was improved significantly by limiting the separation concentration of the spiral chute and adjusting the position of collecting slider in time. Caustic starch as flotation inhibitor and GK68 as flotation collector were added to the stirred tank at one time before. Now caustic starch is added to the stirred tank and the flotation tank of third-scavenging separately， and GK68 is added to the stirred tank and the cleaning flotation tank separately. After the optimization of various process technologies， the grade of total concentrate is stable at around 65% with the qualified rate of concentrate increasing from 32% to over 80%， and the grade of tailings reduced by more than 2 percentage points. The process optimization effect is remarkable.

Key words: Ultra-low-grade hematite, Grinding, Cyclone classification, Gravity separation by spiral chute, Flotation