Abstract: To study the effect of blend ratio on the quality of yarn especially its tensile performance, a series of cotton/colored cotton/ spun silk blend yarns in different blend ratio were spun by three fiber materials, naturally brown colored cotton, white cotton and spun silk fiber based on technological study of spinning processing. Properties of blend yarns with different blend ratio were tested. The results indicated that with the spun silk content increasing, the tensile strength and elongation at break of yarn were significantly increased, and yarn physical performances such as yarn unevenness, thin and thick were improved significantly, while neps and hairiness of the yarn had no significant impact. The addition of spun silk can generally improve the performance of naturally colored cotton blend yarns.