One of the most effective methods of analysing a single pile and pile groups under lateral loading is Strain Wedge Model (SWM). SWM has a number of advantages in comparison with traditional p-y curves, but this model could traditionally only be used to analyse piles under monotonic loads. In the present paper, SWM has been modified to consider dynamic lateral loading. Based on this new method, called Seismic Strain Wedge Model (SSWM), a computer code has been developed for lateral analysis of piles. Using this computer code, some case studies have been analysed and the results show good agreement with test data. This paper introduces SSWM as a simple and powerful solution to analyse piles under lateral seismic loading.