The study on pinhole closure of diagnostic pinhole in the cavity heated by radiation is reported. Laser Wavelength of 1. 053 μm, energy 300-400 J, pulse width -800 ps with Gaussian shape are used in the experiments. Two laser beams drive the Cavity target with two source regions. The sub-keV X-ray spectrum from source region and implosion region were measured by two sub-keV X-ray energy spectrometers respectively through laser incidence hole and diagnostic hole. The pinhole closure problom was qualitatively analysed and discussed.