Abstract: Processing methods that take floating datum as reference datum have been commnly applied to seismic data processing in areas with large surface altitude difference. Two correction methods regressing to horizontal reference daturn and the correction formulas are given in this paper to process and map these data. In order to eliminate the influence of packing speed, a method to establish average velocity field of high accuracy is presented. It is pointed out that attention should be given to the types of reference datum in interpretation, otherwise ralative large difference of structure feature can create pitfalls in exploratory drilling.