Using tensile test of ZK60 magnesium alloy, the superplastic flow behavior was studied. The deformation temperature was set as 280°C, 310°C,340°C, 370°C and 400°C while strain rate was 1×10-1s-1, 1×10-2s-1, 1×10-3s-1 and 1×10-4s-1. The results showed that the perfect superplastic behavior was presented at 370°C and =1×10-4s-1 and the maximum elongation could be 133.7%. The biggest factor of strain rate sensitivity was 0.62. The microstructure of the fracture was analyzed used SEM and the results showed that the main deformation mechanism of ZK60 magnesium alloy was grain boundary sliding.