The probability of flight conflict is increased because of the increasing of flight flow and uncertainty of flight route.Considering the problem of redundant operation caused by a large number of non-related objects,a preprocessing algorithm for use before conflict detection was proposed.The objects within the surveillance scope of ADS-B IN were divided into 26 different regions,and the correlation of the objects with the own aircraft was distinguished by the specialized rule of each region.Then the correlated objects were further processed,while the uncorrelated ones were blocked.Therefore,the calculation burden for estimation of surrounding traffic situation safety was decreased.The processing principle was “safety the first,” and “better false alarm,never missed alarm”.Finally,the necessity and validity of the proposed algorithm were examined by using Monte Carlo experiment.The simulation results showed that not less than 30% of 30 random objects were blocked.The proposed algorithm is effective and accurate for detecting the correlation between targets.