Abstract: The treatment of simulated radioactive wastewater by direct contact membrane distillation(DCMD) process with polypropylene hollow fibers was conducted to estimate the effect of feed temperature, cooling water temperature, feed velocity, and cooling water velocity on the permeation flux and rejection of objective elements(Sr(Ⅱ), Co(Ⅱ) and Cs(Ⅰ)). Simultaneously, the mechanism of mass transfer and heat transfer was investigated. Among the four operation parameters, the variation of feed temperature shows the highest influence on the permeation flux. The permeation flux increases from 2.7 L/(m²•h) to 29.2 L/(m²•h) when feed temperature varies from 40 ℃ to 80 ℃. In this DCMD process, the mass transfer of vapor in membrane pores is dominated by the Knudsen-molecule diffusion, and the main resistance of mass transfer is derived from membrane itself. In the investigated conditions, i.e., feed temperature(40-80 ℃), cooling water temperature(10-30 ℃), feed velocity(425-1450 mL/min), and cooling water velocity(75-600 mL/min), the decontamination factors(DF) of Sr(Ⅱ), Co(Ⅱ) and Cs(Ⅰ) in the DCMD processes are higher than 10⁵. The experimental results reveal that DCMD process shows excellent treatment effici-ency on the simulated radioactive wastewater, and it can potentially serve as a new method to treat radioactive wastewater.