A three-dimensional theory is developed for a linear cascade oscillating in a supersonic uniform flow between parallel walls to predict the effect of sound absorbing wall liners on the unsteady aerodynamic forces. A side wall of the model is partially composed of a sound absorbing liner with uniform acoustic admittance. The lined section of the wall is confined to the portion swept by blades. Substantial variation of the total aerodynamic work with change in the wall admittance is found to occur only in a confined effective range of the admittance magnitude. The effective range is located in a smaller admittance magnitude and the wall liner effect is larger and more complex for a supersonic cascade compared with a subsonic cascade. The effective range moves to the smaller admittance magnitude as the Mach number increases.