The foam phosphogypsum with low bulk density has been prepared. The influence of retarder content and water-cement ratio on the setting time and strength of phosphogypsum paste, and the effect of water-reducing agent and bulk density on the strength of foam phosphogypsum have been studied. The mechanical behavior and thermal conductivity of the foam phosphogypsum have also been researched. Besides, the failure curve of the as-prepared foam is plastic-like which is different from the brittle failure of normal foam concrete. And the high energy absorption effect of the samples has also been found.