Large power current drive of lower hybrid wave （LHW） was performed （PLHW 100—800 kW at 2.45 GHz） recently in the HT-7 tokamak. The lower hybrid current drive （LHCD） efficiency is studied for different injected powers and for different densities. Improved particle confinement is observed by application of LHCD as characterized by an increase of central line average electron density and decrease of Dα emission. The particle confinement time τp increased about 1.5 times compared with ohm discharge. The dependence of energy confinement time τE on plasma density and LHW power is experimentally studied in detail.