Abstract: According to the design requirements of heat pump evaporating system of nuclear power plant, a set of testing installation was built and corresponding performances and efficiencies of separating process were researched. The results show as follows: the reflux ratio of evaporation and concentration in concentrate has low impact on separating efficiencies of the testing installation. The boron concentration in distillate is less than 0.2 mg/L, which is much lower than the most strict limit value（2 mg/L） of releasing to the environment. The results of radioactive alternative test by using Mg SO₄, show that the decontamination factor of the test installation reaches 105. Generally, the performance of separating and decontaminating of test installation is much better than similar devices as known, which provided the feasibility of near-zero releasing for inland nuclear plant.