i-base superalloys with different Ta contents were prepared by the screw selecting method. The effects of Ta on microstructure and creep mechanism of Ni-base single crystal superalloys were investigated. Results show that the morphology of g ￠ phase changes from ellipse to square with the increasing of Ta content. Negative mismatch of the superalloy increases due to more Ta and Mo dissolved into g phase. The creep rupture time is prolonged and dislocation net in g/g ￠ interface is improved when the content of Ta increases form 6wt% to 10wt%.