An internal lobe pump is suitable for oil hydraulics of machine tools, automotive engines, compressors, constructions and other various applications. In particular, the pump is an essential machine element of an automotive engine to feed lubricant oil. The subject of this paper is the theoretical analysis of internal lobe pump whose the main components are the rotors: usually the outer one is characterized by lobes with elliptical shape, while the inner rotor profile is determined as conjugate to the other. And the integrated system which is composed of three main modules has been developed through AutoLISP under AutoCAD circumstance. It generates new lobe profile and calculates automatically the flow rate and flow rate irregularity according to the lobe profile generated. Results obtained from the analysis enable the designer and manufacturer of oil pump to be more efficient in this field.