A method for the design of new rotor profiles for high-sealing lobe pump is presented in this paper. The objective of this paper is to improve the sealing of lobe pumps by designing chamber profile conforming rotors. The deviation function method is adopted and the resultant rotor profiles are trapping-free and have C1 continuity. A design procedure for rotor generation is also developed. A sealing index is defined to evaluate the sealing property of lobe pumps. Our results show that it is possible to design many new rotor profiles that have better sealing property than conventional involute rotors.