Cooperative spectrum monitoring with multiple sensors has been deemed as an efficient mechanism for improving the moni-toring accuracy and enlarging the monitoring area in wireless sensor networks.However,there exists redundancy among the spectrum data collected by a sensor node within a data collection period,which may reduce the data uploading efficiency.In this paper,we inves-tigate the inter-data commonality detection which describes how much two data have in common.We define common segment set and divide it into six categories firstly,then a method to measure a common segment set is conducted by extracting commonality between two files.Moreover,the existing algorithms fail in finding a good common segment set,so Common Data Measurement(CDM)al-gorithm that can identify a good common segment set based on inter-data commonality detection is proposed.Theoretical analysis proves that CDM algorithm achieves a good measurement for the commonality between two strings.In addition,we conduct an syn-thetic dataset which are produced randomly.Numerical results shows that CDM algorithm can get better performance in measuring com-monality between two binary files compared with Greedy-String-Tiling(GST)algorithm and simple greedy algorithm.