Helicity is a physical parameter describing the rotation movement along the air flow on the environmental wind field and the intensity of movement, can reflect and be used to describe the nature and features of atmospheric circulation. A review is made on the development in theoretical helicity researches and its application from the aspects of the expanding of application domain, the improvement of helicity theory, and the shortages and problems in application. The analysis results show that there exits close relation between helicity and torrential rain processes. The high helicity might be one of mechanisms for rain storm development, and the variation of helicity intensity gives a good clue to torrential rain occurrence. The prospects of helicity research and application are discussed.