Abstract: ‍ ‍Aiming at the problem that TDCS signal is difficult to detect， a detection method based on secondary processing of power spectrum is designed. The secondary power spectrum function of TDCS signal was theoretically deduced by mathematical modeling. Moreover， the secondary power spectrum of TDCS signal was proved that has the characteristics of periodic peaks， and the relationship between the spectral peak period and the basis function period was given. Accordingly， a TDCS signal detection algorithm is designed， which can detect the TDCS signal and estimate the period of the basis function. Through computer simulation， the performance of the algorithm under low signal-to-noise ratio was verified， and the detection performance of the secondary power spectrum method and the time-domain correlation method were compared. The simulation results show that under the condition of low signal-to-noise ratio， the algorithm proposed in this paper is still effective in estimating the period of the basis function， and the performance of the algorithm is improved by about 1.5 dB compared with the autocorrelation method. In addition， increasing the number of sampling points can further improve the accuracy of the secondary power spectrum algorithm.