Quasi-static　mechanical　properties　of　aramid　fibres　reinforced　natural　rubber/SBR　composites　are　comprehensively　investigated　via　scanning　electron　microscopy　(SEM),　uniaxial　tensile　tests,　multi-step　stress　relaxation,　and　the　Mullins　experiment.　The　strength,　stiffness,　viscoelasticity,　and　Mullins　effect　of　composites　are　analysed,　and　the　micro　failure　mechanism　is　also　explored.　It　is　shown　that　the　samples　appear　similar　to　a　laminate　plate　with　random　short　fibres　in　a　plane.　The　results　of　the　uniaxial　tensile　tests　indicate　that　the　tensile　strength　and　elongation　at　failure　decrease,　while　the　stiffness　increases　following　the　addition　of　a　small　amount　of　aramid　fibres　into　the　rubber　matrix.　The　multi-step　relaxation　and　Mullins　experiments　reveal　that　the　aramid-short-fibres　weaken　the　viscoelasticity　of　rubber　composites.　Finally,　the　strain　energy　of　the　composite　is　divided　into　four　parts,　and　one　part　is　considered　with　respect　to　its　application　to　the　study　of　interface　destruction　between　the　matrix　and　fibre.