Based on the double control criterion of displacement and energy, a new index, dynamical damage index, for describing the dynamical damage extent in the single layer latticed shell structure is set up. The calculate method and change law of all kinds of consuming energy under the seismic action in the latticed shell structures are studied. Then the expression of dynamical damage index erected by combining the plastic consuming energy and maximum displacement is present. Moreover, the compare among the three index, dynamical damage index, displacement and plastic bar quantity, is completed by large numbers of parameter analysis in the single latticed shell structures. The results show that the discrepancy of analytical conclusion is distinct among the three index, dynamical damage index, displacement and plastic bar quantity to the latticed shell with local weakening stiffness, and the results of dynamical damage index are more reasonable. The dynamical failure index is in effect for the quantificational analysis of dynamical failure for single layer latticed shells.