In this paper,a physical model of lepidocrocite-TiO2 and GaSe 2D crystals are established.The calculation of the band structure,density of states and optical spectrums of these crystals are performed with the first-principles density functional theory(DFT).The influence of the biaxial stress to the band structure and optical response of the 2D crystals are calculated.The results show that the band gap can be tuned systematically via the biaxial stress.There is a.This study paves the path for these 2D crystals′ further application in tunable electronic devices and photovoltaic devices.