The PTT (Poly Trimethylene Terephthalate) fiber has been used widely in the clothing field for its excellent performance, but the application of its short fibers blended fabric needs to be further researched. At present, cotton fabrics and modal fabrics are chosen to make thin underwear. In this paper, PTT/Viloft/Spandex, JC/PTT/ Spandex, Modal/PTT/ Spandex, FI-R/PTT/ Spandex and Linen/PTT/C/ Spandex blended knitted fabrics of same count are chosen to study. Their air permeability, moisture permeability, thermal resistance, wicking are tested and evaluated. And gray pertinence method is chosen to make comprehensive evaluation on heat-moisture comfort performance of fabrics, the result is that Linen/PTT/C/ Spandex blended fabric has the best heat-moisture comfort performance. It provids certain theoretical support for the application of knitted fabrics made from PTT blended fabrics in the field of underwear.