Since there is only one exponential formula which is used to adjust the rheological convergence rate in the exponential rheological model of 3 parameters, 6 parameters, 7 parameters and Merchant model and H-K model, the deformation of rockfill dam in early impounding period and later impounding period cannot be reflected reasonably at the same time. While the 9 parameters power function rheological model, which can reflect the deformation of rockfill dam well, is inconvenient for mathematical operation. By the way of analogy with compound exponential formula for thermal and mechanical of concrete, a compound exponential rheological model, which can better reflect the rheological deformation law of rockfill dam and is convenient for mathematical operation, is advised from phenomenological perspective, and the finite element calculation formula is deduced based on compound exponential rheological model. Example analysis shows that only taking two compound exponential formulae, with two exponential coordinate adjustment, can better reflect the rheological deformation law of rockfill dam and is convenient for mathematical operation. While one exponential formula is a special case of compound exponential formula, and it cannot reflect the deformation of rockfill dam in later impounding period well.