The invention relates to a method for improving performance of conventional Q&P steel by carbon-manganese comprehensive partition. The method comprises the following steps of: heating a material to certain temperature between AC3 and AC1 (two phase regions) with a certain rate and keeping the temperature for certain time, and quickly heating the material to a temperature higher than AC3 and keeping the temperature for certain time; reducing the temperature to a certain temperature which is between AC3 and AC1 (two phase regions) and is higher than a first manganese partition temperature, and keeping the temperature for certain time, quickly transferring the material to certain temperature between MS and Mf to perform quenching and heat-preserving for certain time; and finally, performing water-quenching on the material until the room temperature. The method adopts a carbon-manganese comprehensive partition process for improving stability of residual austenite though an element carbon and an element manganese, improves the structure and the mechanical properties of the conventional Q&P steel through the comprehensive effect of the element carbon and the element manganese very well; the improved Q&P steel is applied to a car, so that weight of the car body can be reduced, and therefore, the safety is improved; besides, the method further reduces production cost, achieves energy conservation and emission reduction and is wide in application prospect.