Laser cladding deposited Ti–6Al–4V titanium alloy universally shows more complex microstructures,each of which has significant effect on mechanical properties. Of particular α/β interface phase has been observed in this paper under certain conditions. It demonstrates that the influence of the α/β interface phase on the tensile properties is closely associated with dislocations and twin substructure through comparison experiments. The results show that the α/β interface phase hinders dislocation motion and decreases effective slip length. In addition, the twin substructure has been activated in the α/β interface phase during tensile process and has acted somehow like grain boundaries. Therefore, the strength and the work-hardening rate of the laser cladding deposited Ti–6Al–4V titanium alloy have been significantly improved due to the dynamic Hall–Petch effect. Besides, the α/β interface phase leads to more uniform dislocations distribution, which implies that relative lower local concentrated stress will be produced along the α/β interface phase or colony boundary after the same amount of plastic deformation. Moreover,the twinning-induced plasticity effects in the α/β interface phase further increase the plastic deformation capacity. These results in higher elongation for the laser cladding deposited Ti–6Al–4V titanium alloy.It can be concluded that the current work suggests an effective method to simultaneously improve the strength and plasticity of laser cladding deposited Ti–6Al–4V titanium alloy based on the α/β interface phase. Laser cladding deposited Ti-6Al-4V titanium alloy universally shows more complex microstructures, each of which has significant effect on mechanical properties. Of particular α / β interface phase has been observed in this paper under certain conditions. It demonstrates that the influence of the α / β interface phase on the tensile properties is closely associated with dislocations and twin substructure through comparison experiments. The results show that the α / β interface phase hinders dislocation motion and decreases the effective slip length. the α / β interface phase during tensile process and has acted somehow like to grain boundaries. Therefore, the strength and the work-hardening rate of the laser cladding deposited Ti-6Al-4V titanium alloy have been significantly improved due to the dynamic Hall-Petch effect. Besides, the α / β interface phase leads to more uniform dislocations distribution, which implies that relati ve lower local concentrated stress will be produced along the α / β interface phase or colony boundary after the same amount of plastic deformation. These, twinning-induced plasticity effects in the α / β interface phase further increase the plastic deformation capacity. These results in higher elongation for the laser cladding deposited Ti-6Al-4V titanium alloy. It can be concluded that the current work suggests an effective method to simultaneously improve the strength and plasticity of laser cladding deposited Ti-6Al-4V titanium alloy based on the α / β interface phase.