We report on the effect of seed layers thickness on the synthesis of one dimensional (1D) ZnO rods using chemical bath deposition method. This procedure allows us to control the length and diameter of 1D ZnO rods in a large size range by modifying the ZnO seed layer thickness. With the increase in thickness of the seed layer, the length of the 1D ZnO rods ranges from 13.1μm to 2.1μm, and the diameter varies from 2.4μm to 102nm, meanwhile the laying 1D ZnO rods standup gradually. Photoluminescence measurements indicate that the near band edge emission of the 1D ZnO rods blueshift to higher energy direction with the increasing seed layers thickness.