The invention discloses a multi-carrier accomplishing method and device of time-division synchronization code division multiple access system. The method comprises: modulating downlink single speed time domain signal to frequency domain signal through quick Fourier transform, performing spectrum shift and rooted raised cosine filter for frequency domain signal, then performing reverse quick Fourier transform to produce downlink N carrier time domain signal, interpolating the downlink N carrier time domain signal to produce K speed signal then low pass filtering. The inventive TD-SCDMA multi-carrier accomplishes combination on DSP, so a radio frequency can accomplish multi-carrier function. Multi-carrier filtering separately accomplish on DSP and FPGA, DSP can accomplish RRC filtering, FPGA can accomplish low pass filtering. Transmission time delay controls digital signal and continuous phase of frequency domain which enables high precision algorithm and low complexity.