Abstract: This paper describes a method for the preparation of macroaggregated albumin (MAA) kits which is labelled with 99mTc for lung scanning.The tween-80 is used as both dispersing agent and stable agent in order to raise uniformity and concentration of MAA particle size, which is between 10 to 100μm. More than 80% particles are in the range of 10-60nm. A millilitre MAA solution contains 5.3 × 108 particles. The lyophilized MAA kits are stable within eight months. The unlyophilized MAA kits are stable within 51 days.The radiochemical yield is>95% and the radiochemical purity is determined by paper chromatography. In addition, centrifuge method is used in combination with micro paper chromatography, in order to obtain the percentage of 99mTc(Ⅳ) bound to the MAA, the percentage of unreduced "free" 99mTc(Ⅶ) and the percentage of reduced-hydrolyzed form of 99nTc(Ⅳ) .Blank centrifuge test of the 99mTc(Ⅳ)-Sn colloid shows that about 85% 99mTc(Ⅳ) is found in the supernatant solution. This method is simple and rapid. After eight hours the radiochemical purity of the labelled 99mTc-MAA sample placed at 16 ℃ and 22 ℃ remains>95%.The organ distribution of LACA 18-26g mice meets the standard of the same product in the US pharmacopeia. The results of the study with rabbits by scanning with γ-camera indicate that the activity in the lung of the rabbit reaches a high level between 2-3 hours after injection. The toxic test and nonsterile and nonpyrogen test are very satisfactory and meet the standard of the Chinese pharmacopeia.