The invention discloses a method for producing iron-nickel-copper alloy micro-powder by treating nickel waste slag in an oxidizing atmosphere furnace, and belongs to the field of ore dressing. The method comprises the following steps of: preparing the nickel waste slag, a reducing agent and an additive according to the mass proportion of 100:(15-30):(5-25) as the raw materials, crushing or milling the above raw materials for uniform mixing, loading the mixture into a kiln container, sealing the container, loading the container into the oxidizing atmosphere furnace, roasting the container for certain time at certain reducing temperature, cooling and discharging the reduced furnace burden, crushing and wet milling the discharged furnace burden, and carrying out magnetic separation treatment on the milled furnace burden to obtain the iron-nickel-copper alloy micro-powder. The tailings after the iron-nickel-copper alloy micro-powder is selected can be used as the raw material for extracting tabular spar, firing a hollow brick or partially replacing clay for calcining cement clinker. By adopting the method disclosed by the invention, iron, nickel and copper in a lot of ferric metasilicate, which cannot be separated by the traditional technology, can be extracted, and can be converted into the iron-nickel-copper alloy micro-powder with high added value, and the problems of air pollution caused by insufficient fuel utilization and reducing tail gas, reaction adhesion of the material with the kiln container wall and the like are prevented.