Abstract: How to realize high speed data transmission and high precision measurement in a limited frequency band is a problem confronted by navigation & communication integrated systems. In this paper, a new modulation, named multi-carrier binary offset carrier (MC-BOC) modulation, is presented by combining the orthogonally frequency division modulation and constant envelope modulation. The modulation can improve the spectral efficiency and the receiving performance, and also have the characteristics of constant envelope. Performance of radio determination satellite service(RDSS) signal adopting the proposed modulation is analyzed, and the results show that MC-BOC modulation has good data demodulation, ranging, anti-jamming, and anti-multipath performances. The new modulation provides a solution to signal design and optimization for navigation & communication systems.