Abstract: In this paper, firstly the cooperating system of shear wall, shear wall on flexible support and walled frame with stepped cross—section are simplified as a Timoshenko canti—lever beam on continuouselastic foundation with spring supports at the bottom end. Equations of horizontal vibration have been derived. Secondly, using the ODE (Ordinary Differential Equation) Solver, which is a program developed for solving various ODE, the fore five vibration frequencies and vibration modes have been obtained.