Flexible, stretchable and sensitive textile-based sensors play important roles in a wide variety of artificial intelligence because of its seamless integration with clothing and good comfort. Herein, MXene sensing layer is deposited on the surface of springlike helical core-sheath polyester yarns thanks to the capillarity effect and its intrinsic hydrophilic ability, and the resultant strain sensor and humidity sensor exhibit wide detection range from 0.3 to 120% strain and 30-100% relative humidity (RH) detection, owing to elastic core-sheath structures. The strain sensor shows excellent reproducibility (over 10000 cycles) and fast response time (120 ms). The core-sheath yarn sensor can detect various human motions such as walking, bending and twisting as well as physiological signal (pulse), which have great potential in real-time precise medicine and health care. The yarn sensor could also be an excellent humidity sensor because of the high specific area structure of yarn and intrinsic hydrophilic properties of MXene sensing layer.