Spin-polarized plasma induced by the radiative spin flips in ultrarelativistic laser-matter interaction attracts great attention. Spin-polarized electron beams are broadly utilized in probing the structure of solid-state materials, exploring nucleon structure, and facilitating the analyses of the electroweak interaction. Electron spin, an intrinsic property of the electrons, could provide a new degree of freedom of information in characterizing plasma collective behaviors. In this manuscript, we review the mechanism of the production of radiative spin-polarized plasma and discuss its potential application in retrieving the transient ultrarelativistic plasmas.