Abstract: In order to explore the dynamic constitutive relationship of ultra-high toughness cementitious composites (UHTCC) and the influence of fiber volume fraction on dynamic mechanical properties of polyvinyl alcohol (PVA) reinforced cementitious composites (PVAFRCC), the compressive impact tests were carried out on PVAFRCC specimens with different fiber volume fractions (0vol%, 0.5vol%, 1vol%, 1.5vol%, 2vol%) by using Φ80 mm split Hopkinson pressure bar (SHPB) system, through which the stress-strain curves of various types of materials at different strain rates were obtained. The results show that: compared with the matrix without fiber added (PVAFRCC-0), the incorporation of PVA fiber has a significant effect on the dynamic increase factor ( \mu _\rmDIF ), impact toughness and crushing resistance capacity when the strain rates range from between 100-270 \rms^-1 , which will be further enhanced with the increase of fiber volume fraction. The impact toughness is more sensitive to strain rate than to fiber volume fraction. Compared with the matrix, the \mu _\rmDIF and impact toughness increase by nearly 33%-37% and 27%-33% respectively when the fiber volume fraction equals 2vol% (PVAFRCC-2), and the average fragments size of PVAFRCC-2 also increases to 5.9~6.8 times of that of the matrix. On the basis of Weibull distribution theory, the dynamic constitutive model suitable for UHTCC specimens with 2vol% PVA fiber volume fraction was proposed and verified.