The present invention discloses a duplex stainless steel and a thermal processing method thereof, belongs to the technical field of duplex stainless steel thermal processing, and solves the problem inthe prior art that duplex stainless steel is prone to generating surface cracks or edge cracks during thermal processing. The method comprises: raising a duplex stainless steel casting blank to 800 DEG C from the charging temperature, to realize a first temperature rise; raising the temperature from 800 DEG C to 980 DEG C, to realize a second temperature raise; raising the temperature from 980 DEG C to 1180-1200 DEG C, to realize a third temperature raise; the second temperature raise rate is greater than the first temperature raise rate, and the third temperature rise rate is less than the second temperature raise rate. The thermal processing method of the duplex stainless steel can be used for thermal processing of the duplex stainless steel.