Deuterium retention behavior in W-Fe-Ni alloy was investigated by the gas-phase driven permeation system and thermal desorption tests. The deuterium permeability, diffusion coefficient, solubility, and diffusion activation energy of deuterium in the W-Fe-Ni alloys were investigated. The thermal deuterium charging and thermal deuterium desorption experiments were conducted. Combined with the microstructure characteristics and numerical simulation, the deuterium retention behavior in W-Fe-Ni alloys was studied and the diffusion model of hydrogen isotope in W-Fe-Ni alloy was established to predict the deuterium retention in W-Fe-Ni alloys with different shapes. Compared with the results of thermal desorption tests, the amount of hydrogen isotope retention in W-Fe-Ni alloy can be accurately estimated by the multi-physics field numerical simulation.