A novel wideband multi-resolution spectrum sensing method is presented in this paper. By exploiting the frequency aliasing effect caused by multi-rate down-sampling, the spectrum activities of multi-channels can be inferred from the resulted spectrum-aliased sample streams. A specially designed Belief Propagation (BP) algorithm is adopted to conduct the above inferring. Simulation results show that this spectrum sensing method has excellent performance. To the best of our knowledge, it is the first algorithm to do multi-channel spectrum sensing based on multi-rate down-sampling and frequency aliasing.