Roots vacuum pump is one of the dry type pump without oil lubrication. It has been widely used in the equipment for semi-conductor process due to high speed development of the semi-conductor industry. However, the pump performance of the domestic products is always worse than the abroad ones, wherein the key technology is the design of rotor profiles. Therefore, this project aims to develop one type of novel and high efficient rotor profile which is consisted of circular arc, extended cycloid and involute. The specifics of this novel rotor include: the cycloid section is generated by a variable extended-distance point attached on a variable-radius rolling circle, with a tip sealing arc, high adjustable flexibility of tooth profile and the area usage coefficient can achieve higher than 0.43. Besides, this project will propose a new index, airtight area, and its calculation method to estimate the inner leakage degree of vacuum pump. The developed rotors for a vacuum pump will be manufactured and tested by a cooperative company to prove its advantages.