Abstarct: Dynamic analysis of structures is generally utilized to study the behavior and response of structures against dynamic loads. Earthquake load is one of the most important types of dynamic loads which is applied to structures. Dynamic analysis of structures against earthquake loads is mostly performed baxsed on two methods: Spectral & Time-history methods. In Spectral method the maximum response of structures is taken into account, whereas in Time-history method the entire response of structures as a function of time is considered. Although Time-history method is more accurate than Spectral method, due to the fact that long time is consumed in Time-history method, its applications are limited to only special structures. The aim of this thesis is to reduce the time of analysis in Time-history method using the filtration of seismic waves. In the proposed approach only low frequency components of earthquake wave which have high energy are selected as the baxse of dynamic analysis and therefore, the analysis time is considerably reduced. Two filtration process of earthquake wave were performed and the last components of low path, which have the lowest frequencies, were selected for dynamic analysis. It was observed that the analysis time was reduced to a quarter of the original time with sufficient accuracy.Filtering was made by using baxse wavelet function.in each step of filtering the size of component containing low frequency is half of the previous size.After performing dynamic analysis for low frequency component and finding the structural response to this component,inverse wavelet transform of response is calculated to compare this response with original response. Decompositionof the origional wave was made by two types of wavelet(i.e daubechies and haar),it was found that the analysis error is less when using daubechies wavelet compare to haar wavelet.the response of structure to the high frequency componeny is also calculated.it was found that in this case the response is very different from the response to the oigional earthquake.consequently the high frequency component is not a representive of the original earthquake.