Plant　straw　fibers　have　been　used　widely　in　composite　materials　as　reinforcement　due　to　their　advantages　of　low　density,　easy　degradation,　low　cost,　and　abundance.　However,　the　mechanical　properties　and　water　resistance　of　the　as-prepared　composites　are　limited　due　to　the　poor　compatibility　between　plant　straw　fibers　and　polymer　matrix.　In　this　work,　the　rice　straw　fibers　were　pretreated　with　the　silane　coupling　agent,　lipase,　and　hydrothermal,　and　then　blended　with　phenolic　resin　to　prepare　composites.　The　results　showed　that　the　pretreatment　of　the　fibers　can　improve　their　compatibility　with　the　resin　matrix　and　improve　the　comprehensive　mechanical　properties　and　the　thickness　swelling　of　composites.　When　the　mass　ratio　of　fiber　to　resin　is　1:1　and　the　hot-pressing　condition　is　160°C　and　11 min,　the　static　bending　strength,　elastic　modulus,　and　thickness　swelling　of　the　phenolic　resin/lipase-treatment　rice　straw　fibers　(PF/L-SF)　composite　reached　23.03 MPa　and　2588.39 MPa,　which　increased　by　32.9%　and　30.5%　compared　with　the　unmodified　fiber/phenolic　resin　composite　(PF/SF).　Copyright　©　2022　Zhou,　Chen,　Huang,　Lin　and　Ye.