Abstract: The feasibility of direct labeling of chondroitin sulfate (CS) with ⁹⁹Tc^m was studied, and the effects of different conditions on labeling yield was observed，and the biodistribution of ⁹⁹Tc^m-CS in normal mice was investigated, chondroitin sulfate was labeled directly with ⁹⁹Tc^m reduction of ⁹⁹Tc^mO₄ with SnCl₂ solution. The labeling yield and radiochemical purity were determined with thin layer chromatography （TLC）using Xinhua filter paper. The biodistribution of ⁹⁹Tc^m-CS in normal mice was studied at 30 min, 1, 2, 4 and 8 h respectively after caudal vein injection in normal mice. The labeling yield was 81.6％±1.7％ and radiochemical purity was 90.1％±1.2％ after filtering by micropore membrane.The biodistribution in mice showed that ⁹⁹Tc^m-CS was cleaned out from blood quickly, and it was mainly excreted through kidney, but ⁹⁹Tc^m-CShad high specificity to cartilage go blood was 8.31（4 h）, the ratio of cartilage to bone was 2.03(4 h). ⁹⁹Tc^m-CS is an easily prepared and labeled compound with high philo-cartilage and stability.