This research aimed to study the lengths effect of calculated filter- operator by inverse filtering on the seismic data filtering. All programs used for estimating the seismic signal, calculate the Filter- operator and performing the Convolution were written by author. Some experiences about the influence of the length of filter-operator of the outcomes of the inverse filtering were performed. The seismic data used in this research were measured in two different areas in Syria, Alsaegh dam nearby Sueda City and Rajo dam nearby Aleppo City. In addition, experiences are carried out to test the effect of shortening the length of filter-operator. The results showed that small length of filter-operators can be used by inverse filtering without negative effect on the resolution of seismogram. In addition we noticed that shortening the length of filter-operator depend on the length of calculated filter-operator.