Abstract: The finite element analysis(FEA) program ANSYS is used to analyse 20 000m3 oil tank.It is calculated the seismic response of loop and vertical stresses of tank wall and base moment with change in liquid height in tank.So seismic properties are analyzed,and compared with code and simplified measures to testify its validity.It is shown from the results that seasonally frozen ground evidently influences site dynamical characteristics and seismic security of tank.On non_frozen ground the tank is secure both on basic intensity and rare intensity,while on frozen ground the tank is secure on basic intensity and is not secure on rare intensity.