Earthquake source parameters have important impact on the near-fault ground motions and their spatial distribution characteristics. Using a discrete wavenumber finite element method, we simulate the ground motion fields, and then study the effect of fault depth on ground motion amplitude, spectra and duration from the directivity point of view. Numerical results show that: with increasing fault depths, the amplitude decreases but the difference between forward and backward direction still exists; the significantly affected areas is getting closer to the fault; and the radiation angle of directivity effect gradually extends to both sides of the fault strike. This phenomenon indicates that the source depth not only affect the amplitude of ground motion but also the significantly affected areas and locations. Therefore, the source depth parameter should be considered in the prediction of ground motion in engineering, especially in near-fault region.