The influence of Cobalt, Tungsten, and Titanium on stress-rupture properties of Nickel-base single crystal superalloy has been investigated using orthogonal arrays experimental design. The compositions of alloy have been optimized by mathematical analysis. The results show that Ti content has the most important influence on persistent lives and it is followed by Co, W in the effects. The persistent life is long when the alloy contains 10wt%Co, 8wt%W and 0wt%Ti. This alloy also has high microstructure stability after long-term ageing.