In order to study the effect of different blended ratios on strength and elongation properties of Outlast/viscose blended yarn, ten kinds of blended yarns had been designed and spun. The blended ratios were Outlast/viscose 0/100, 15/85, 25/75, 30/70, 35/65, 40/60, 45/55, 50/50, 60/40, 100/0. By testing the strength and elongation properties of the blended yarn, the effect of blended ratio on blended yarn’s breaking tenacity and elongation rate was analysed. The results showed that, with the increase of blended ratio, the breaking tenacity and breaking elongation rate of the blended yarn both presented a downward trend. But when Outlast/viscose blended ratio was 35:65, breaking elongation rate had a maximum value. When blended ratio was 45:55, breaking tenacity had a maximum value, which should be used in practice.