In order to study the influence of sudden drawdown of dam water level on the void of high concrete face rockfill dam(CFRD), the paper chose the material constitutive model and the contact surface model between the panel and the dam through the system analysis and comparison.It proposed the simulation method of dam construction loading ,storage process and slab voidsi. Taking a concrete faced rockfill dam as an example, according to different drop speeds and amplitude of dam water level,the paper made four kinds of schemes,and respectively conducted the calculation of dam three-dimensional finite element stress deformation and void simulation. Then, through analyzing the calculation result of four calculation schemes, the paper systematicly summarized the law of influence of dam water level drawdown speed and amplitude on force deformation and void of CFRD. The results showed that in the condition that the decline of dam water level is fixed, with the decrease of speed of water drop,the panel void value decreases;in the condition that the drawdown speed of water level is fixed, with the decrease of water drop amplitude, the panel void value also decreases；therefore, in the construction of concrete face rockfill dam ,it is necessary to control the speed and amplitude of smaller water level drop of dam so as to prevent the further development of panel void phenomenon.