Abstract: Three kinds of uranium targets, solution-dried target, powder target and block target, were chosen to preliminarily study the release ratios of krypton and xenon fission products. After irradiated in Xi’an pulsed experiment reactor, the krypton and xenon products were released in normal-pressure-circular mode and adsorption-vacuum mode. An indirect approach was used to determine the ultimate release ratios of them. The solid product was used to determine the total fission number which was used to calculate the atom number of the krypton or xenon products. When the release atom number was determined by measuring the released gas product, the release ratio was expressed as the ratio of above two values. The results show that there is large difference of the release ratios in three kinds of targets and the lowest release ratio in block targets. So the release ratio is tightly correlative with the chemical form of target. At the same time, the independent yield of the gas product is also an important factor to the release ratio.