The invention discloses a comprehensive treatment method of waste water from laterite-nickel ore wet smelting, which comprises the following steps: adjusting magnesium-containing waste water to be neutral so as to return the waste water to the ore-washing or leaching procedure for a process purpose, increasing the magnesium concentration of the waste water to above 50 g / L, performing heavy metal removal and manganese removal, performing negative pressure evaporation concentration, cooling crystallization, centrifugation separation, and drying to obtain magnesium sulfate heptahydrate, performing magnesium precipitation of the mother liquor after crystallization by sodium carbonate, separating basic magnesium carbonate, performing negative pressure evaporation concentration, cooling crystallization, centrifugation separation, and drying of the mother liquor after magnesium precipitation to obtain sodium sulfate decahydrate, or returning the mother liquor after magnesium precipitation directly to the iron-removing procedure of the nickel-extraction flow and to be used as a sodium source for iron removal by a sodium jarosite method. The method of the invention is simple and practical,has low cost, does not generate waste by-products, can both produce salable chemical products and reduce the production cost of the main flow for nickel recovery, and also prevents environment pollution.