Trial spinning was done at 11 blending ratios (of Outlast fiber/cotton), namely 0/100, 10/90, 20/80, 30/70, 40/60, 50/50, 60/40, 70/30, 80/20, 90/10 & 100/0. By test, analysis and calculation to the targets of breaking strength, moisture regain, fusion enthalpy, crystallization enthalpy, etc. and curve simulation to them with origin7.5, an unique objective function was set in the way of objective optimization. Then lingo9.0 was applied to determine the optimal blending ratio of Outlast fiber/cotton blending yarn and it was concluded that at about 60% of Outlast fiber content, the ratio is the best, i.e. the blending yarn has the best targets in general.