This paper studied the rock dynamic fracture propagation under impact loads elab-orately with a determination method proposed to calculate crack propagation dynamic stress intensity factor(DSIF).By utilizing the split-Hopkinson pressure bar,the impact experiments with an improved single cleavage semi-circle(ISCSC)specimen were conducted to illuminate the dynamic crack propagation behaviour.Meanwhile,the fracture characteristics and crack propa-gation velocity were obtained by the crack propagation gauges.Coordinating experiments with a numerical approach,the crack propagation dynamic stress intensity factors were calculated by an experimental-numerical method with fractal theory.Then,a finite difference model was developed based on the tensile fracture softening damage criterion.With the analysis of numer-ical and experimental results,the crack propagation behaviour and mechanism of crack arrest were discussed sophisticatedly.The results demonstrate that the novel ISCSC specimen shows a definite advantage in determining crack propagation and arrest DSIF.Additionally,the crack arrest DSIF is larger than the average propagation DSIF with a sharp increase.Meanwhile,the numerical simulation results which agree well with the actual crack propagation illustrate that the crack arrest should be dominated by the compressive stress perpendicular to the crack path,and there were several arrest pauses existing in the transitory crack arrest process.