Effect of solution and aging heat treatment on microstructures and stress rupture properties of a fourth generation Ni-based single crystal superalloy with content of 4.0% (in weight percent) Re and Ru has been investigated.The results show that the as-cast alloy exists significant composition segregation.Due to less Al and Ti elements, interdendritic γ/γ’ eutectic content is low.During the solution heat treatment,the eutectic is almost dissolution after 1310℃.However,the differences between dendrite core and interdendritic is completely eliminated until 1340℃ and the segregation of other elements except Re is significantly improved.The advantage of the fourth generation Ni-based single crystal is to improve the mechanical propertie at high temperature,especially stress rupture properties.After solution and aging heat treatment,the stress rupture lives of DD476 is about twice that of the second generation single crystal superalloy at 950℃/300MPa and is more than 10 times comparaed with the second generation single crystal superalloy MC2 at 1150℃/100MPa.There is no TCP(topologically close-packed) precipitation during the whole heat treatment because of the addition of Ru element in DD476.