Relationship　of　densities　between　Cf/SiC　composites　and　C/C　preforms　was　studied　by　theoretical　calculation.　And　2D　Cf/SiC　composites　were　prepared　from　three　kinds　of　C/C　preforms　with　densities　of　0.98,　1.06,　1.12　g/cm3,　which　were　prepared　by　repeatedly　overlapping　the　layers　of　carbon　cloths　and　precursor　infiltration　pyrolysis,　by　liquid　silicon　infiltration.　The　effects　of　densities　of　C/C　preforms　on　structure　and　property　of　composites　were　study.　The　results　were　compared　with　theoretical　calculation　results.　The　research　results　show　that　the　test　results　are　basically　consistent　with　the　theoretical　mathematical　results.　The　density　of　Cf/SiC　composites　increases　first　and　then　decreases　with　the　increase　of　the　C/C　preforms　density.　And　when　the　density　of　C/C　preform　is　greater　than　0.98　g/cm3,　the　flexural　strength　of　composites　decreases　with　the　increase　of　C/C　preforms　density.　The　composites　have　a　better　structure　and　property,　while　the　density　of　C/C　preforms　is　0.98　g/cm3.　©　2016,　BUAA　Culture　Media　Group　Ltd.　All　right　reserved.