The seat frame is a component of the car seat, consisting of various beams, boxes, and plates made of structural steel. The seat frame transmits forces from the vehicle floor to the seat. Finite element analysis simulations in Ansys Workbench were used to assess the strength, deflection, and maximum stress characteristics of the car seat in two stages. In the first stage, simulations in Matlab Simulink were conducted to determine the forces acting on the seat as a harmonic function. In the second stage, finite element analysis was used to identify the maximum stress and deflection on the seat leg frame in both the initial case and the case equipped with an energy-absorbing cushion. The results of the simulation indicate that when the vehicle travels over bumpy roads with sinusoidal speed bumps, there are sudden increases in high-amplitude impact forces that could damage the seat. According to the simulation results regarding the deformation and stress conditions of the seat components, the location with the highest stress of 318 MPa was identified, exceeding the allowable stress of 270 MPa by 17.8%. After improving the seat frame structure by adding an energy-absorbing cushion at the assembly location with the vehicle floor, the maximum stress was reduced to 231 MPa, thereby ensuring compliance with safety standards.