Abstract: Linear introduction accelerator is expected to generate small diameter xray spots with high intensity． The interaction of the electron beam with plasmas generated at the xray converter will make the spot on target increase with time and debase the x ray dose and the imaging resolving power. A distributed target is developed which has about 24 pieces of thin 0.05mm tantalum films distributed over 1cm． Due to the structure adoption, the distributed target material over a large volume decreases the energy deposition per unit volume and hence reduces the temperature of target surface, then reduces the initial plasma formalizing and its expansion velocity. In this paper, the comparison and analysis with two kinds of target structures are presented using numerical calculation and experimen