In cognitive radio system, the licensed spectrum resource that is not been used by the primary users could be reused opportunistically by the unlicensed secondary users. Spectrum sensing is the fundamental task in cognitive radio system for the secondary system should detect the available idle spectrum resource accurately and timely. Performance of traditional blind spectrum sensing is limited by the channel fading and noise uncertainty, especially under low SNR environment. Based on the Gaussian Noise suppression feature of high order statistical analysis, a novel spectrum sensing approach is provided based on the simplified Bispectrum slide analysis. Simulations have shown that our approach performs much better than the commonly used energy detector in noisy environment with little more complexity, and the sensing technology is quite appropriate to detect the wireless broadcast TV signal and wireless microphone signals under low SNR environment.