To be effectively heated in incinerator for MSW is very important for stabilization and completeness combustion, the smaller produce of the PCDD/Fs. At the same time, the transient heat transfer characteristics of the MSW lump decides the stay time of the MSW in incinerator and effects on the operation feature of the combustion equipments. All of these would lead to design the reasonable and clean combustion project, the optimum incinerator and recover energy system. The component, shape, dimension, property, the hardly and inner structure feature of the MSW lump are taken in account, and the effective conduct heat coefficient has been adopted. And then, the physical model is setup with different shape(ball, cylinder, squareness), and the 3-D mathematical model and conduct heat efficient with porous feature for transient heat transfer of MSW lump are presented, at the same time, the simulation tests are gotten in various boundary and the interesting conclusions are gotten: The center stable temperature of the MSW lump is mostly decided by the inner gas temperature of the incinerator and the heated area of the lump. The transient heat transfer characteristics is variously effected by the shape of the MSW lump in incinerator. The transient process becomes longer and the center stable temperature decreases, the volatile can't be easily separated out and the combustion efficiency decreases because of the increasing of the lump feature dimension.