In order to prevent unseating during earthquakes， both domestic and foreign seismic codes for bridges require the use of unseating prevention devices. However， research on the effectiveness of these devices is limited. This article focuses on a bridge us? ing a longitudinal barrier-type unseating prevention beam device， examining the limitations and effectiveness of such devices in pre? venting unseating. First， the working principle of the longitudinal barrier-type unseating prevention device is introduced. On this ba? sis， a five-span simply supported beam bridge is studied， considering the nonlinear mechanical behavior of concrete blocks as a typi? cal longitudinal barrier-type unseating prevention device. The study analyzes and compares the effects of block device strength， clearance， and the installation of rubber pads on the limiting and unseating prevention capabilities of the device. Research has shown that the effectiveness of the devices is closely related to its strength ，initial clearance， and the intensity of seismic motion. Proper device strength and initial clearance can help reduce collision forces and frequencies， lower the risk of beam unseating， and control bridge pier damage within an ideal range. Furthermore， placing buffer rubber pads at the contact surfaces between the un? seating prevention device and the substructure can effectively reduce pounding forces and minimize pier damage.