Li doped CuO films are prepared on glass substrate by pulsed laser deposition，and the effect of Li doping on the structure and properties of CuO films is studied. The crystallinity of CuO films becomes better when Li doping concentration increases from 0 wt% to 2 wt%，and then becomes worse when Li doping concentration increases from 2 wt% to 3 wt%. After doping Li，the carrier concentration increases by at least three orders of magnitude，and it shows a trend of first increasing and then decreasing. The change of mobility is just the opposite. When the doping concentration is 2 wt%，the carrier concentration reaches the maximum，which is 1.10×1019 cm-3，and the resistivity is as low as 76 Ω·cm. This is mainly due to the fact that Li atoms enter different lattice positions of CuO when doped with different concentrations of Li.The electrical and optical properties of CuO thin films doped with Li have been improved to some extent，which provides theoretical guidance for further research of CuO thin film solar cells.