Freestanding honeycomb borophene is unstable due to the electron-deficiency of boron atoms.B2H2 monolayer,a typical borophene hydride,has been predicted to be structurally stable and attracts great attention.Here,we investigate the electronic structures of B2H2 nanoribbons.Based on first-principles calculations,we have found that all narrow armchair nanoribbons with and without mirror symmetry (ANR-s and ANR-as,respectively) are semiconducting.The energy gap has a relation with the width of the ribbon.When the ribbon is getting wider,the gap disappears.The zigzag ribbons without mirror symmetry (ZNR-as) have the same trend.But the zigzag ribbons with mirror symmetry (ZNR-s) are always metallic.We have also found that the metallic ANR-as and ZNR-s can be switched to semiconducting by applying a tensile strain along the nanoribbon.A gap of 1.10 eV is opened under 16％ strain for the 11.0-(A) ANR-as.Structural stability under such a large strain has also been confirmed.The flexible band tunability of B2H2 nanoribbon increases its possibility of potential applications in nanodevices.