The traditional method of generating pseudorandom phase vector through a linear feedback shift register (LFSR) and a preset combination of taps in transform domain communication system(TDCS) was studied. Based on the requirements of the pseudorandom phase vector in TDCS, a new method using chaos mapping to generate the pseudorandom phases in TDCS was proposed. This method generated binary quantization chaotic sequences by using chaos mapping with different initial values, and then creates a pseudorandom phase vector by using a phase mapper. Finally, the basis function was obtained. The implementation method of chaos mapping and the simulation results regarding the correlation performance for the basis function were discussed in detail. Compared with the basis functions generated by LFSR, the basis functions generated by chaos mapping have better correlation performance. Because many basis functions with small crosscorrelation coefficients can be generated by chaos mapping, this method is advantageous for multiple access applications.