Abstract: Improved double disk targets are used to investigate X-ray re-emission from gold material heated by radiation. The primary disk is an oblique cylinder cavity. X-ray radiation emitted from the Au foil in the rear of the cavity ablates secondary Au disk. Thus plasma expan sion's effect of primary disk on secondary disk is reduced, and then the X-ray radiation ablating secondary disk is “pure and clear”. An X-ray streak camera is used to measure time-space images of double disk targets. Two soft X-ray spectrometers are used to measure X-ray spectra of primary and secondary disk respectively. The property that X-ray spectra were modified on secondary disk is investigated. The measured results show that the improved double disk targets can basically avoid plasma expansion's effect from primar