Known as one of the Cognitive Radio (CR) transceiver technologies, the transform domain communication system (TDCS) has the characteristic of 1ow probability of intercept (LPI) and the capability of multiple access (MA). In this paper, basing on the random phase mapping, the characteristics of the pseudorandom (PR) phase vector and the Basis Function (BF) are investigated. After that, two methods of generating random phase, the least common multiple method and the equal interval method are proposed, which both can generate the PR phase vector and the BF of TDCS. In matlab, simulation results indicate that the two methods both can generate the BFs, which have the characteristic of strong autocorrelation and weak crosscorrelation in TDCS.