Cognizing　the　structural　characteristics　of　a　heterointerface　is　significant　to　understand　the　growth　mechanism　of　heterostructured　nanowires.　Here,　the　structural　characteristics　of　a　heterointerface　in　GaAs-GaAsSb　heterostructured　nanowires　were　investigated　by　employing　spherical　aberration　(C-S)-corrected　transmission　electron　microscopy　(TEM).　It　is　found　that　some　unusual　dislocations　are　formed　at　the　heterointerface,　leading　to　the　bending　of　nanowires.　Further,　the　atomically　inhomogeneous　distribution　of　Sb　content　near　the　heterointerface　is　revealed,　which　is　responsible　for　the　formation　of　dislocations.　By　applying　a　thermal　electric　system　equipped　in　the　Cs-corrected　TEM,　a　direct　observation　of　structural　evolution　at　the　heterointerface　was　enabled　and　the　stability　of　GaAs-GaAsSb　heterostructured　nanowires　was　evaluated.　In　situ　high-resolution　TEM　imaging　indicates　that　the　destabilization　of　the　heterointerface　occurs　during　nanowire　annealing.　This　study　builds　a　direct　correlation　between　the　nanowire　heterointerfacial　structure　with　nanowire　growth　behavior　and　its　stability,　which　is　of　importance　for　heterostructured　nanowire　design　for　practical　use.