The　concrete　compositions　have　great　effects　on　the　drying　shrinkage　behavior　of　ultra-high　performance　concrete　(UHPC).　Five　factors　including　water-to-binder　ratio　(w/b)　and　contents　of　steel　fiber,　superplasticizer,　silica　fume　and　fly　ash　were　considered　to　evaluate　their　influences　on　the　drying　shrinkage　behaviors　of　UHPC　in　this　investigation.　Based　on　the　drying　shrinkage　test　results,　the　effect　degrees　of　these　factors　were　analyzed　by　the　gray　relation　entropy　analysis.　Then　the　microstructure　and　pore　distributions　of　UHPC　samples　were　measured　by　scanning　electron　microscope　and　mercury　intrusion　porosimetry　for　mechanism　analyses.　The　results　reveal　that　a　lower　w/b　or　higher　content　of　fly　ash　is　conducive　to　achieving　a　reduction　in　drying　shrinkage　of　UHPC,　while　the　additions　of　superplasticizer　and　silica　fume　have　an　adverse　effect　on　drying　shrinkage,　resulting　in　increased　drying　shrinkage,　and　the　effect　of　steel　fiber　on　drying　shrinkage　is　not　monotonic,　its　optimum　dosage　is　50　kg/m3　in　this　work　and　a　lower　or　higher　amount　will　cause　an　increased　DSS　of　UHPC　compared　with　the　one　with　an　optimum　dosage.　The　five　factors　can　affect　the　drying　shrinkage　behavior　of　UHPC　by　principally　changing　the　microtopography　and　internal　pore　structure　of　the　concrete　matrix,　according　to　the　gray　relation　entropy　analysis,　the　effect　degrees　of　studied　factors　on　drying　shrinkage　of　UHPC　are　as　follows:　w/b　＞　superplasticizer　＞　silica　fume　＞　fly　ash　＞　steel　fiber.　©　2022　Elsevier　Ltd