Abstract: A femtosecond Ti:sapphire chirped pulse amplifier with multipass amplification was developed in this paper, new concepts on overcoming gainnarrowing and enhancing amplification efficience are also introduced. Pulses of 25fs duration with 36mJ energy have been produced at repetition rates of 10Hz only under 290mJ doubled frequency Nd:YAG laser pump, which corresponds to 1.4TW peak power．