With　the　rapid　development　of　wearable　intelligent　devices,　traditional　rigid　strain　sensors　can　no　longer　meet　the　requirements　of　wearable　technology　for　high　strain　detection,　and　it　is　urgent　to　develop　new　flexible　strain　sensors.　The　sponge-based　piezoresistive　strain　sensors　based　on　polymer　and　nano-conductive　materials　have　the　remarkable　characteristics　of　light　weight,　good　flexibility　and　stretchability,　simple　fabrication　and　low　cost.　The　research　progress　of　flexible　strain　sensors　based　on　polyurethane　sponge,　graphene　sponge,　PDMS　sponge　and　so　on　in　recent　years　was　reviewed　from　the　perspective　of　substrate　materials.　It　was　pointed　out　that　the　preparation　of　flexible　strain　sensors　with　high　sensitivity,　wide　detection　range,　fast　response,　good　cycle　stability　and　robust　device　performance　is　still　a　challenge.　©　2021,　Editorial　Board　of　Polymer　Materials　Science　&　Engineering.　All　right　reserved.