International　roughness　index　has　become　a　well-recognized　standard　for　measurement　of　pavement　roughness　in　the　world.　In　China,　the　current　evaluation　rules　are　such　that　the　average　value　of　IRI　measured　from　road　test　sections　is　used　to　evaluate　road　quality.　However　this　evaluation　method　is　not　proper　in　judging　road　quality　in　practical　application.　In　this　study,　moment　method　is　utilized　to　statistically　analyze　the　IRI　data　distribution　of　expressway　pavement.　In　Beijing　city,　8　expressways　of　different　road　ages　are　selected　as　test　samples,　and　then　a　time　series　of　IRI　data　are　employed.　By　statistical　analysis,　a　comprehensive　evaluation　system,　which　is　composed　of　3　indictors　such　as　the　average　of　IRI,　skewness　coefficient　and　kurtosis　coefficient　is　established.　Practical　application　testified　that　the　evaluation　system　can　truly　reflect　expressway　riding　quality.　©　2009　ASCE.