The　cellulose　fiber　(ultra-fiber　500)　is　a　new　type　natural　cellulose　fiber.　In　order　to　study　the　flexural　toughness　of　cellulose　fiber　reinforced　concrete,　the　flexural　toughness　experiments　of　concrete　with　synthetic,　steel　fibers,　and　hybrid　fiber　are　made　at　the　same　time,　and　the　load-deflection　curve　of　all　beams　are　obtained.　Based　on　the　ASTM　method,　the　flexural　toughness　of　concrete　with　cellulose,　synthetic,　steel　fibers　and　hybrid　fibers　are　all　analyzed.　The　experimental　results　indicate　that　the　cellulose　fiber　can　improve　the　flexural　toughness　and　the　deformation　ability　of　concrete　beams.　The　flexural　toughness　index　I5　and　I10　of　concrete　with　cellulose　fiber　are　3.0　and　5.8　times　higher　than　that　of　the　plain　concrete　respectively.　For　the　same　ratio　of　volume　of　fibers,　the　flexural　toughness　index　of　cellulose　fiber　reinforced　concrete　is　higher　than　that　of　concrete　with　PP　fiber.　Cellulose　and　steel　hybrid　fibers　can　improve　the　toughness　and　deformation　ability　of　concrete　remarkably,　and　the　failure　mode　changes　from　brittle　to　ductile　fracture.