Aiming at complex time-varying non-cooperative satellite communication environments with a lower Signal-to-noise Ratio(SNR), a double-channel blind detection algorithm of satellite communication signals based on an energy spectrum and a bispectrum slice is presented. Firstly,the power spectrum is calculated to detect the energy; then,the bispectrum slice is fastly computed by the power spectrum to implement bispectrum detection; finally, the two results are combined. By making use of the second and the third order statistics synchronously, the method increases available information and is favorable to improving the detection performance. Simulation results indicate that detection probability of the method is 10% higher than that of any of the above two in the same lower SNR conditions without adding computational complexity relative to that of energy detection. The presented algorithm can satisfy non-cooperative satellite communication requirements of high speeds, real-time and lower SNRs.