A method for extracting copper, including: 1) inputting a copper cinder into a ball grinder to grind, screening, transferring resulting coarse grains to a first magnetic separator to yield a copper concentrate I and magnetic minerals, and returning the magnetic minerals to the ball grinder; 2) transferring resulting fine grains from the screening to a classifier to yield a deposited sand and an overflowing slurry, returning the deposited sand to the ball grinder, transferring the overflowing slurry to a flotation unit to yield a copper concentrate II and a gangue; 3) transferring the gangue to a second magnetic separator to separate a non-magnetic mineral from a magnetic mineral, transferring the non-magnetic mineral to a gravity concentrator to get a semi-qualified product, and transferring the semi-qualified product to a table concentrator to yield a copper concentration III; 4) discharging the gangue and the magnetic mineral.