In order to get accurate calculation result of seismic interval velocity by use of velocity spectrum,this paper,taking the GeoMountain Seismic Interpreter System as a platform,puts forward a new calculation method of interval velocity including general DIX interval velocity calculation method restricted by regional empirical value,backstepping calculation method through the known interval velocity spectrum based on general DIX formula,horizon-based calculation method of interval velocity and azimuth smoothening etc.Examined by the actual structural map of Mopan-Laowan working area in East Sichuan basin,the interval velocity calculated by this method showed a better rule in lateral variation and coincided better with the actual geological conditions.