Abstract: Study of scroll profiles theory at present mainly is aiming at the single profile and its ameliorate or parameter optimization,not aiming at the nature characteristic of the profiles-equation of scroll profiles itself.For this condition,the intrinsic differential equation bearing on arc-length and tangent direction angle was studied.Using the inherent differential equation and general functional theory,the transform method between intrinsic differential equation and Cartesian coordinate was researched,and the condition of involutes characteristic was presented.Based on the method of Taylor series,the unified formalism of general functional integration molded lines was established,which perfected general theory of scroll profiles increasingly.The detail analysis of four typical scroll profiles was given.The inherent characteristics of scroll profiles model are broken through and the design method of scroll profiles is widen.