Wearable strain sensors have great application prospects in the emerging fields of human motion detection, health monitoring, wearable electronic devices and flexible electronic skin. In recent years, the wearable piezoresistive strain sensors, which are composed of two-dimensional (2D) conductive materials and flexible polymer substrates, have attracted wide attention due to their high sensitivity, good stretchability and flexibility, excellent durability, adjustable strain sensing performance and easy processing characteristics. Based on these, this work reviewed the classifications, sensing mechanisms, performance indexes, influence factors and applications of wearable piezoresistive strain sensors based on 2D conductive material/flexible polymer composites (2D-CPC). Finally, the future development trend of the strain sensors is also prospected.