Considering the noise characteristics of the pump source　the noise spectra of ou tput harmonic field from the singly resonant frequency doubler is derived by mea ns of the motion equations for SHG.The intensity noise squeezing of 20% has been measured from the stable SH wave output.(It is in accordence with the squeezing of 30% if the efficiency of detection system is taken into account).The maximum squeezing measured experimentally is in agreement with the theoretical predicti ons.