Abstract: The 3.3MeV accelerator of Southwest Institute of Fluid Physics is a linear induc-tion accelerator(LIA),whose electron beam parameters are 2kA,3.3MeV and 90ns,built in1991.This accelerator was disigned to drive the SG-I free electron laser.This paper describesbriefly the accelerator and the SG-IFEL facility.The emphases will be placed on the modifica-tion to the pulsed power system of the linac and beam conditioning section of the SG-Iin orderto satisfy the needs for the FEL experiments.The beam current entering the wiggler has been in-creased.Beam quality and system reliability and stability are also improved.Beam parametershave been given at different position. The two important parameters for FEL,beam emittance andenergy spread,are 0.43 cm· rad and 1% respectively.The beam current through the space and ener-gy spread selector into the interaction region is about 950A. The ASE FEL output is about100kW.The amplified FEL output of above 10MW power and gain of 20dB/m have been obtained.