Abstract: A kit for preparing ~(99)Tc~m-SAA(small albumin aggregates) is obtained by heating the HSA solution and freeze-drying the product. The particle size detected by electron microscope is smaller than 80 nm which is suitable for bone marrow, inflammation and lymph imaging. The labeling yield with Na~(99)Tc~mO_4 is more than 99% and the labeling is stable within 4 hours. The biodistribution in mice shows that the ~(99)Tc~m-SAA excretes mostly from the urinary tract. High concentration of radioactivity in liver, spleen and marrow are observed and the bone marrow can be seen clearly from 30 to 60 minute after injection in rabbit imaging. The labeling method is simple,~(99)Tc~m-SAA has desirable stability, higher uptake in marrow and may serve promising as a new colloid imaging agent.