Bright green light in the amplitude-squeezed state is experimentally generated from a frequency doubler with semi-monolithic F-P configuration consisting of an a-cut type-Ⅱ KTP crystal and a concave mirror. The amplitude-squeezing of 3.1±0.2dB at 540nm wavelength is obtained with the pump power of 50mW under the conditions of the two infrared modes in resonance and the green mode nearly in resonance.