The ground motion speed and displacement caused by earthquake dynamic effects have a greater influence on long-period structures, and the vibration mode decomposition response spectrum method is unable to make an accurate assessment. Therefore, we introduced the concept of shear-weight ratio. The relationships between the shear-weight ratio, the earthquake influence coefficient and the effective mass coefficient through simplifying the shear-weight ratio were also obtained. Through specific engineering examples, three adjustment processes of shear-weight ratio made by software SATWE of SATWE series based on the seismic code were shown. The study provides a novel method for the analysis of earthquake dynamic effects.