In order to investigate the dynamic shear failure mechanism and size effect law of deep concrete beams with Basalt Fiber Reinforced Polymer （BFRP） bars， a three-dimensional meso-scale numerical model of BFRP reinforced concrete deep beams was established considering concrete heterogeneity， concrete /BFRP reinforcement interaction， and strain rate effect of concrete and BFRP bars in material level. Firstly， the rationality and accuracy of the numerical simulation method are verified by the existing experimental data. Then， the shear failure modes and failure mechanisms of the geometrical-similar BFRP-reinforced concrete deep beams with different sizes under different strain rates were studied by the numerical simulation method. The influence of beam depth， stirrup ratio and strain rate on the shear failure of BFRPreinforced concrete deep beams and the corresponding size effect law were analyzed. The results indicate that： The failure modes of beams under dynamic loading are different from those under static loading， but they all show size effect； Both the strain rate and the stirrup rate can effectively improve the bearing capacity of the beam and weaken the shear size effect， but the effect of strain rate is significantly greater than that of stirrup rate.