Abstract: In view of data processing in complex surface area, the method of floating datum for static correction is usually used to minimize the distortion of the hyperbolic characteristic of reflected events resulting from severe fluctuation in static correction, so that the accuracy of volocity analysis, the signal/noise ratio and even the quality of reflection image of seismic data can be improved.Based on theoretical analysis of present correctiom method on floating datum, a new method for establishing floating datum using fold number imformation which can overcome some defects in traditional method is given in this paper.Practical data processing shows that the method has an advantage over the traditional one in reflecting geological structures rationaly and reliably