Abstract The tight binding method was used to calculate the band structures of and its nanoribbon structures. We studied the influences of the quantum confinement effect and the strain effect to the band structure. The tensile strains were applied on both the confined and the transport directions of the nanoribbon. We found that the bandgap and the effective mass decrease with an increasing strain. In addition, the tensile strain along the transport direction has a better effect on reducing the hole effective mass. Although external strains can reduce the carrier effective mass, the valence band edge actually changes from the K valley to the valley with a significantly larger effective mass. Sructure profile (real space and k‐space) and valence band maximum under different tensile strains.