Abstract: Separation level of non-volatile radioactive substances was analyzed by theoretical method,and specially designed purification tower was tested.The results showed that the experimental result was unanimous of which was gained by theoretical method.So the theoretical method and calculation model were rational.The theoretical model was applied on the evaporation equipment in the liquid waste treatment TEU system of a nuclear power plant,and the results showed that 3 sieve plates with wire mesh demister was rational and it could satisfy the requirement of nuclear power plant with a high safety margin.