When sensor networks are deployed in mission-critical applications such as target detection,data fusion technologies can significantly improve sensing coverage.Based on the probabilistic sensing model with an exponential decay factor,the paper analyzes the intrinsic relationship between data fusion and coverage performance.The paper also proposes some definitions,including node virtual radius,fusing-cover,to quantize the improvement on network coverage performance caused by data fusion.The effect of data fusion on node density, where sensor nodes are deployed virtually in the regular polygon way,is evaluated.On the base of above theoretical analysis,a virtual radius based coverage algorithm to schedule sensor nodes is designed to guarantee every interest point in the region being either covered,or fusing-covered.The theoretical analysis indicates that the number of nodes which are participated in fusion process within virtual radius must be less than six.Otherwise,data fusion does not reduce the node density,and has a negative effect on the node density.The experimental result demonstrates that the proposed method can efficiently improve the coverage performance and prolong sensor network’s lifetime.