For the instability of the system caused by parameter changes， this study investigates the filtering problem of closed-loop pole placement under region constraints，and a filtering system design method based on output feedback is proposed. In the presence of uncertainties in both the controlled system and the feedback filtering system， the solvability condition of the output feedback filtering system is given in the form of linear matrix inequalities. This condition ensures asymptotic stability of the closed-loop system， suppression of filtering error output with respect to changes below a given upper bound， and the proper placement of closed-loop system poles in a specified region on the complex plane. This method is used to simulate and verify the longitudinal motion of a certain type of police unmanned aircraft. The distribution of closed-loop system poles is within the expected limits， indicating that the system is asymptotically stable and achieves the design objective. This demonstrates the effectiveness of the proposed method.