Objective To invent a filling valve for filling corrosive solution. Methods Breaking the traditional design concept of metal filling valve, plastic filling valve used polymer plastic as its main structure material, which utilized the flexible and tensile characteristics of plastic valve-stem. When the valve-stem was pulled up , the filling valve was closed. Simultaneously, at the end of the valve-stem the valve core and guiding valve-body formed hermetical loop-line. When the valve-stem was pushed down, the filling valve was opened. In addition, a spring was installed on top of the filling valve to ensure that the valve stay close in case of gas path fault, to avoid liquid leakage. Results Plastic filling valve was not only corrosion resistant to strong acid and strong alkali but also had many other merits such as reasonable structure, higher security, higher reliability and lower manufacturing cost. Conclusion Plastic filling valve successfully solved the problem of filling corrosive liquid in the field of chemical industry.