To get the accurate measurement of the equation of state (EOS) by using the laser-driven shock wave, it is necessary to guarantee the stability of shock propagation in sample target. Using one dimensional radiation hydrodynamics code MULTI, the stability of the shock wave propagation in planar Al targets driven by the laser power densities of 8.1×1013 W/cm ,with 1.053 μm wavelength, 1ns Gaussian pulse width is studied. The simulation results show that thickness of the substrate should be greater than the shock waves acceleration propagation distance, and the thickness of the sample should be approximately equal to the shock waves stable propagation distance in the design of impedance-match targets, in order to ensure the average velocity of shock waves in the sample approximately equals to the stable transmission velocity.