The invention relates to a process for stage grinding full-permanent magnet short-flow treatment of mixed iron ore. The process comprises the following steps that crude ores with a grade being 29.00%-30.00% and a particle size being below 2 mm are fed in a primary closed-circuit grinder; primary grading overflow with a content of -200-mesh ore being 60%-65% is fed in a primary permanent magnet machine; primary magnetic concentrates are fed in a secondary closed-circuit grinder; secondary grading overflow with a content of -200-mesh ore being 90%-95% is fed in a secondary permanent magnet machine; secondary magnetic concentrates are fed in a ternary permanent magnet machine; ternary magnetic concentrates are final concentrates with a grade being 63.7%-65.50%; primary magnetic tailings, secondary magnetic tailings and ternary magnetic tailings are merged as final tailings with a grade being 10.10%-10.60%; and the iron recovery rate is 75.7%-77.70%. The process has the following advantages that the permanent magnet machines with efficient performances and simple structures are adopted; an existing beneficiation process flow for treating mixed iron ores is simplified and optimized; thecost is reduced; and the economical benefit is obvious.