A hybrid method [1] is used to solve the wave of 3-D low Reynolds flow in an elastc pipe. The flow region is divided into far field and near fielf. In far field the solutions can be expressed by series expansions[2], while in the near field FEM could be used. 3-D eigen-functions must be taken into account. The corresponding eigen values are calculated numerically. It is shown that except the fundamental eigen functions which are just the 2-D ones, the others decrease very quickly. So 2-D eigen functions are enough for many cases.