Spectrum sensing is one of the most challenging tasks in cognitive radio. Unfortunately traditional schemes fail to balance between accuracy and complexity, which are the key indicators for the performance of spectrum sensing. In this paper, a new spectrum sensing scheme based on phase difference is proposed. Through analyzing the distributions of phase difference between adjacent samples of noise and noise-perturbed primary signal, we notice that the mean of phase difference varies from noise when primary signal is present. On this basis, a novel sensing scheme using the accumulation of phase difference as test statistics is formulated. Then the analytical performance of our scheme is derived and its complexity is analyzed. Our proposed scheme is simple, accurate and immune to noise uncertainty. Simulation results show that our scheme outperforms conventional energy detection and can achieve a detection probability of 99% at −7dB signal-to-noise ratio using 500 data samples.