This paper studies the intensity distribution inside the frequency conversion crystals when the continuous phase plate (CPP) is placed in 1ω light of final optics assembly for inertial confinement fusion (ICF) driver. Our study shows that the modulation of 1ω light caused by CPP makes the frequency conversion efficiency and the uniformity of intensity field inside the frequency conversion crystals decrease. It leads to the possibility of laser induced damage for frequency conversion crystals to increase. What worth paying special attention to is: the modulation and maximum intensity in the vicinity of entrance and exit surface of frequency conversion crystal is much higher than in other areas, so the possibility of laser induced damage is also relatively greater there. However, if the intensity of 1ω light before the frequency conversion system becomes even greater, for the normal running of final optics assembly the modulation and maximum intensity inside the frequency conversion crystals should be confined within the permitted range.