The integration-test-bed (ITB) device is established for research on inertial confinement fusion(ICF) in China. The single-beam output energy reaches 19.6 kJ successfully when the fundamental frequency emission wavelength is 1053 nm and the pulsewidth is 5 ns. Experimental results of thermal effect of 400 mm × 400 mm aperture slab amplifiers in ITB devices show that the peak-to-valley value dPV of pump-induced wave-distortion of the whole laser chain is about 5.3 l, in the revise extension of deformable mirror, when the gain coefficient is 5.28% cm^-1. Combined with the optimizations of heat management, the thermal recovery time is about 2.5 h, which can satisfy the requirement of 4 h/shot.