The Kalman filtering theory was applied for the back analysis of mechanical parameters of mass concrete on the first time. The time-spreading equation and the observation-correcting equation were deduced. After the coupling problem of extending Kalman filtering theory and FEM was solved, the Kalman-FEM formula were deduced and the corresponding back analysis procedures were given. The results indicate that the Kalman filtering method has good characteristics of convergence and stability. The broached method can be used in other research fields such as the back analysis of creeping parameters. Many more conclusions are tested and discussed through a classic example.