Abstract: To evaluate dynamic effects of progressive collapse and determine dynamic magnification factor for large-span single-layer spatial grid structures, a model of single degree of freedom was developed in this study. The principles of dynamic magnification considering initial conditions were derived when the sub-structures were elastic and elastic-plastic. The theories in this paper were validated through numerical examples. The simplified simulation method of dynamic effect, suitable for single-layer spatial grid structures, was put forward. On this basis, the value ranges of the dynamic magnification factor of single-layer latticed shells were given. The analytical results show that, neglecting initial conditions, the trend of the displacement and load dynamic magnification factor was consistent when the structures were elastic. With the development of the plastic area, the load dynamic magnification factor decreases and the displacement dynamic magnification factor increases respectively. It is obvious that initial conditions should be considered as the dynamic magnification factors considering initial conditions are smaller than those calculated when not considering the initial conditions. Furthermore, it is suggested that the load dynamic magnification factor should be 1.7~1.9 when the demand for the capacity ratio (DCR) is less than 0.7 and 1.4~1.6 when DCR is greater than 0.9 for single-layer latticed shells.