The invention discloses a treatment method for deeply removing thallium and cadmium from smelting wastewater. The treatment method comprises the following steps: S1, preparing a reagent A from 5-18% of sodium dimethyl dithiocarbamate, 5-15% of sodium tripolyphosphate and 1-5% of sodium sulfide nonahydrate; S2, preparing a reagent B from 20-45% of polyferric sulfate and 10-30% of polyaluminum chloride; S3, carrying out primary treatment: taking smelting pretreatment wastewater, adjusting the pH value of the wastewater to 8-11, adding an oxidant, then adding the reagent A, performing a reactionfor 10-20 min, finally adding the reagent B, performing a reaction for 5-15 min, and then carrying out filter pressing; and S4, carrying out secondary treatment: adjusting the pH value of the primarily filter-pressed solution to 7-10, adding the reagent A, performing a reaction, then adding the reagent B, performing a reaction, standing the obtained solution, and discharging the wastewater after the obtained supernatant is qualified. The method is scientific and reasonable, is safe and convenient to use, is suitable for various smelting pretreatment wastewaters, has wide applicability, and hasthe advantages of good treatment effect on wastewater with low content of thallium and cadmium, high pertinence, short process, simplicity in operation, and short reaction time.