Abstract: Based on the status quo of increasingly upsizing and free standing oil tank, contrastive analysis is conducted for relevant regulations of Chinese and American design standards (GB 50341-2003 and API 650-2012) for large-scale storage tank on the seismic calculation to summarize the differences in the seismic fortification basis, design criteria, mathematical model as well as its parameters and calculation methods. The methods specified in Chinese and American standards produce different seismic calculations for the 5 000 m³ covered floating roof tank in the project. Especially with respect to the critical allowable stress of the tank wall, the difference in calculation results of both standards can be nearly 3 times as large. It is the parameter with the biggest difference of calculation results but also the numerical reflection of different fortification objectives in both standards. GB 50341-2003 specifies the top free space of the storage tank as the sloshing wave height, while API 650-2012 specifies that the top free space of the storage tank shall be determined in full consideration of tank seismic purpose, group and other factors to more accurately define the relationship between the top free space and sloshing wave height of storage tank.