Fibrous　porous　materials　are　the　preferred　absorbers　for　many　applications　since　they　can　absorb　impact　energy　and　sound　waves.　The　microscopic　morphology　and　the　relationship　between　the　compressed　state　and　sound　absorption　characteristics　are　studied　for　compressed　fibrous　porous　materials.　A　series　of　specimens　of　fibrous　porous　materials　are　prepared　and　compressed　to　different　thicknesses,　and　their　pore　size　distributions　are　analyzed.　The　average　pore　size,　dynamic　flow　resistivity,　and　acoustic　impedance　of　the　compressed　fibrous　porous　materials　are　derived　theoretically.　The　effects　of　porosity,　thickness,　average　pore　size,　compression　ratio,　and　combinations　of　these　parameters　on　the　dynamic　flow　resistivity　and　sound　absorption　coefficient　of　compressed　fibrous　porous　materials　are　discussed　theoretically.　It　is　demonstrated　that　the　compression　ratio　decreases　the　sound　absorption　coefficient　of　fibrous　porous　materials.　The　compression　ratio　and　average　pore　size　are　important　factors　for　the　dynamic　flow　resistivity　and　sound　absorption　coefficient.　Our　results　could　help　establish　a　theoretical　foundation　for　understanding　the　microscopic　morphology　of　compressed　fibrous　porous　materials　and　aid　the　design　of　fibrous　porous　materials　for　various　applications.　©　2020　Author(s).