Abstract: Geochemical modeling codes for radionuclide migration play an important role in studying geological disposal of high level radioactive waste. The principles, structures, functions and features of several geochemical modeling codes, i.e. CHEMSPEC, EQ3/6, MINEQL+ and VMINTEQ were compared. The tests of these four codes with several examples show that the different results mainly come from the differences in thermodynamic data bases such as the differences in equilibrium constants, temperature correction data and activity coefficients. For sufficiently dilute solutions under standard state, good agreement is reached for all results obtained from the four modeling codes.