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Lateral two-dimensional (2D) heterostructures have opened up unprecedented opportunities in mode electronic device and material science.In this work,electronic properties of size-dependent MoTe2/WTe2 lateral heterostructures (LHSs) are investigated through the first-principles density functional calculations.The constructed periodic multi-interfaces pattes can also be defined as superlattice structures.Consequently,the direct band gap character remains in all considered LHSs without any exteal modulation,while the gap size changes within little difference range with the building blocks increasing due to the perfect lattice matching.The location of the conduction band minimum (CBM) and the valence band maximum (VBM) will change from P-point to Γ-point when m plus n is a multiple of 3 for A-mn LHSs as a result of Brillouin zone folding.The bandgap located at high symmetry Γ-point is favourable to electron transition,which might be useful to optoelectronic device and could be achieved by band engineering.Type-Ⅱ band alignment occurs in the MoTe2/WTe2 LHSs,for electrons and holes are separated on the opposite domains,which would reduce the recombination rate of the charge carriers and facilitate the quantum efficiency.Moreover,exteal biaxial strain leads to efficient bandgap engineering.MoTe2/WTe2 LHSs could serve as potential candidate materials for next-generation electronic devices.