  PandaX-4T is a ton-scale dark matter direct detection experiment using a
dual-phase TPC technique at the China Jinping Underground Laboratory. Various
ultra-low background technologies have been developed and applied to material
screening for PandaX-4T, including HPGe gamma spectroscopy, ICP-MS, NAA, radon
emanation measurement system, krypton assay station, and alpha detection
system. Low background materials were selected to assemble the detector.
Surface treatment procedures were investigated to further suppress radioactive
background. Combining measured results and Monte Carlo simulation, the total
material background rates of PandaX-4T in the energy region of 1-25
keV$\rm{}_{ee}$ are estimated to be (9.9 $\pm$ 1.9) $\times \ 10^{-3}$ mDRU for
electron recoil and (2.8 $\pm$ 0.6) $\times \ 10^{-4}$ mDRU for nuclear recoil.
In addition, $^{nat}$Kr in the detector is estimated to be <8 ppt.
