Since December 27th 2012, BeiDou Navigation Satellite System has officially provided the navigation services for users in the Asia-Pacific region. Unlike the other legacy Global Navigation Satellite Systems, such as GPS and GLONASS, apart from the Medium Earth Orbit (MEO), BeiDou uses Geostationary (GEO) and Inclined Geosynchonous Orbit (IGSO) satellites. This fact increases the service availablility of the system, but also gives more challenges for BeiDou receivers. This paper introduces a method for calculating the pseudoranges between the Beidou satellites and the receivers. The new method is proved to have less computational complexity, while the quality of the position estimation is similar to that of the traditional methods in literature.