Taking a 30 m-span precast small box beam bridge as the research object, the response spectrum method is used to analyze the seismic performance of small box beam bridges with different site classifications, pier heights of 5~15 m and longitudinal reinforcement ratio of 0.6%~2.1% under E1 and E2 earthquakes in the VII degree zone (0.1g). The research results indicate that the higher the pier height and site classification, the lower the longitudinal reinforcement ratio of the pier column, and the less abundant the strength of the pier column during E1 and E2 earthquakes. The transverse bridge direction of the pier column can be designed as elastic components, while the longitudinal direction can be designed as elastic or ductile components based on the pier height, site classification and reinforcement economy. When the seismic site type is class IV, the anti-sliding capacity of the bearing is insufficient, and the seismic isolation design can be used. The lower the longitudinal reinforcement ratio of pier column and the higher the classification of the site, the greater the displacement of the pier top. The lower the longitudinal reinforcement ratio, the larger the allowable displacement of the pier top. The low piers should be designed as elastic components. The pier columns are designed according to ductile components. The ratio of longitudinal reinforcement ratio of pile to column is 1.21~1.92. The relevant conclusions can be used as reference for similar projects.