Display omitted •SRO existed in Al0.3CoCrFeNi and was manifested by the aggregation of Al-Ni atoms and Cr-Cr atoms.•SRO was positively correlated with the mechanical properties of Al0.3CoCrFeNi.•SRO hindered the full expansion of SFs and enhanced dislocation density.•SRO made the fluctuation of SFE more violent, the dislocation path more tortuous, and the dislocation pinning effect stronger.•The strength and toughness was increased by deformation twins, multisystem slips and nanoscale precipitates. Recent studies show that the atoms in high entropy alloys (HEAs) are not randomly distributed but have a certain short-range order (SRO). However, the study of the effect of SRO on Al0.3CoCrFeNi properties is insufficient. In this paper, the effect of SRO on the mechanical properties of Al0.3CoCrFeNi was investigated by molecular dynamics (MD). Melting/quenching and hybrid Monte Carlo (MC)/MD optimization were used to order the random distribution model. The effects of SRO on tensile and shear properties, stacking fault energy (SFE) and dislocation slip were comparatively analyzed and systematically discussed. The results show that the SRO inhibited the propagation of SFs and enhanced dislocation storage capacity. The ordering of the single crystals promoted the formation of deformation twins. The ordering of the polycrystals leads to martensite, BCC phase transformation, and activation of the sub-slip planes. SRO resulted in more severe SFE fluctuation, a more tortuous dislocation path, and a stronger pinning effect. The strength and toughness enhancement resulted from plane slip, multi-system slip, deformation twins, and nanoscale precipitates.