With the rapid development of unmanned helicopter technology, the unmanned helicopters are used more and more frequently in battlefield. When using the unmanned helicopters to aid the warships for target detection, the detection range can be enlarged greatly, which can supply more comprehensive battlefield information to the commanders. In recent years, Kalman filtering are finding applications in the areas of communication, navigation, guidance and control, and various improved Kalman filtering algorithms have been proposed. In order to improve the detection precision of the unmanned helicopter, a Kalman filtering algorithm based on Monte Carlo method is presented here, and an analysis is made to its precision.