Interstitial　La0.7Pr0.3Fe11.5Si1.5C0.2Hx　hydrides　with　large　magnetocaloric　effect　are　prepared.　It　is　found　that　the　addition　of　carbon　atoms　can　lower　the　rate　of　hydrogen　absorption/release,　which　is　beneficial　to　an　accurate　control　of　hydrogen　content.　The　Curie　temperature　T-C　can　be　adjusted　to　the　room　temperature　by　changing　the　carbon/hydrogen　content.　The　introduction　of　carbon　atoms　leads　to　a　remarkable　reduction　of　thermal/magnetic　hysteresis　because　the　first-order　magnetic　transition　is　weakened.　The　maximal　magnetic　entropy　change　of　La0.7Pr0.3Fe11.5Si1.5C0.2H1.2　is　found　to　be　22.1　J/kg　K　at　T-C　=　321　K　without　hysteresis　loss　for　a　field　change　of　0-5　T.　(C)　2012　Elsevier　B.V.　All　rights　reserved.