Abstract: Tc is a major components in high-level radioactive wastes. The species distribution of Tc is a key factor influencing its transport and deposition behavior in aqueous solution. It is easy to calculate species by using a geochemical computer program. The species distribution of Tc in Beishan groundwater by PHREEQC was calculated. The results show that TcO₄^- is the main species under oxidation condition, and the influence of pH to the existing form of Tc in this case is very small. However, the overwhelming chemical form of Tc under reducing environmental condition (pe=-3—-0.5) depends on the solution pH: TcO(OH)₂ in the pH range 4.6-8.8, and TcO₄^- in higher pH.