A new separation method, wiped molecular distillation (WMD), was applied and experimental work was carried out to study the effect of operation parameters such as distillation temperature, pressure, feed flow rate, wiped speed and the separation stages on purifying the raw material containing 95% 3-hydroxypropionitrile (HPN). It was an excellent result that the mass concentration of HPN in the final product can be more than 99.5% under the optimistic operation conditions. The high purity cannot be achieved with normal separating method includ- ing rectification and extraction in practice. As for the raw material, a function of HPN purity in distillate was plotted with distillation temperature and pressure in experiment ranges. According to the experiment data obtained and the theory in molecular distillation, the distillation speed of HPN and separation efficiency were computed. It was concluded that the distillation speed of HPN and the separation efficiency were satisfying for industrial production. A new separation method, wiped molecular distillation (WMD), was applied and experimental work was carried out to to study the effect of operation parameters such as distillation temperature, pressure, feed flow rate, wiped speed and the separation stages on purifying the raw material containing 95% 3-hydroxypropionitrile (HPN). It was an excellent result that the mass concentration of HPN in the final product can be more than 99.5% under the optimistic operating conditions. The high purity can not be achieved with normal separating method includ- ing rectification As for the raw material, a function of HPN purity in distillate was plotted with distillation temperature and pressure in experiment ranges. According to the experiment data obtained and the theory in molecular distillation, the distillation speed of HPN and separation efficiency were computed. It was concluded that the distillation speed of HPN and the separation efficiency were satisfying for industrial production.