Spectrum　Sensing　is　the　key　technology　of　Cognitive　Radio　(CR).　This　paper　proposes　a　new　cyclostationarity　based　spectrum　sensing　method　with　uncertain　arrivals　of　primary　users.　The　method　first　divides　the　spectrum　sensing　period　of　a　SU　into　several　intervals　according　to　the　reciprocal　of　cyclic　frequency,　then　computes　the　test　statistic　from　these　intervals　based　on　Likelihood　Ratio　Test　(LRT),　calculates　the　threshold　based　on　Newman-Pearson　(N-P)　criteria　and　finally　makes　the　decision.　Simulation　results　demonstrates　the　validity　and　the　superiority　of　the　proposed　method　when　the　PU　comes　uncertainly,　compared　with　the　conventional　cyclostationarity　based　spectrum　sensing　method.