Direct contact membrane distillation (DCMD) was used to treat low level radioactive wastewater (LLRW). The dusty gas model (DGM) was used to analyze the mass transfer mechanism and calculate the permeate flux. The operating parameters such as feed temperature, feed velocity and feed concentration were studied. The experimental results showed that DCMD process can separate almost all Cs+, Sr2+ and Co2+ from wastewater. The permeate flux decreased linearly when NaNO3 concentration increased from 1.0 to 200 g/L. The permeate flux remained about 60% of its initial flux even when NaNO3 concentration in feed solution was as high as 200 g/L. The dusty gas model can be successfully applied to estimate the mass transfer, and the experimental permeate flux values fitted well with that calculated by DGM. DCMD is a promising separation process for low level radioactive wastewater treatment. (C) 2013 Elsevier By. All rights reserved.