Abstract: Flexible nanocomposite piezoresistive strain sensors are becoming more and more attractive owing to their unprecedent merits in sensing performance and stretchability, which can be feasibly employed in the fields of wearable electronics and structural health monitoring.Inthiswork, three aspects including structural design, preparation methods and application prospects are briefly reviewed, where recent progress of composite piezoresistive strain sensors is mainly discussed by centering on materials chosen and structure configuration towards the sensing improvement. Crucial parameters in affecting the sensing performance as well as sensing mechanism have been initially analyzed in composite piezoresistive strain sensors. Subsequently, detailed discussion and analysis were performed on the recent advances of composite strain sensors by focusing on the main guideline of materials optimization-structural design/processing-performance improvement and practical applications. Recent achievements of finite element analysis (FEA) and artificial intelligence algorithm are also introduced to conduct the controlling and mechanism analysis of conductive network design (formation, overlapping and evolution) and multi-scale layered structural configuration in composite strain sensors, where both conductive network and structural configuration are playing a significant role in changing the sensing performance. Consequently, a multi-modality sensor with distinct sensing signal, high stability and low hysteresis is urgently needed to fulfill the demands of flexible nanocomposites for piezoresistive strain sensors, where main points towards future developments and future directions in composites strains sensors are also highlighted.