Abstract: Uniaxial tensile behavior is the important character for studying resistivity and toughening effect of engineering cementitious composites(ECC).Uniaxial tensile test of three ratios UF cellulose fiber reinforced cementitious composites(UF-ECC) and the influence regularity on the mechanical properties of ECC under different fiber content is studied in this paper.The relationship of crack width and tensile stress is researched.Tensile fracture energy and characteristic length are discussed.The result indicates that from 0.3% to 0.6% of UF cellulose fiber in volume, maximum tensile strain, fracture energy and characteristic length for UF-ECC respectively improve 183%, 419% and 281%.The maximum strain of UF-ECC is 8-20 times more than that of polypropylene fiber reinforced concrete. UF cellulose fiber has good resistivity and toughening effect, and significantly improves the cracking resistance and deformability for ECC.ECC can show strain-hardening and multiple cracking performances in uniaxial tensile test.