Abstract: Taking advantage of the theory of chemical vapour transfer reaction, the formation thermodynamics of vapour complex NauTavClu+5v was experimentally investigated in closed Pyrex ampoules as reactors at 588-663 K under 0.06-0.12 MPa for about 6 h by way of high-temperature phase equilibrium quenching. The results showed that the ln(PNaTaCl6)/P^⊖ vs. ln(PTaCl5)/P^⊖ plot and lnKp vs. 1/T plot are both in linear relation and the vapour complex NaTaCl6 is the sole reaction product from tantalum chloride and sodium chloride. The thermodynamic equilibrium constants of the reaction are all determined from experimental result. Based on the stability constant obtained at different temperatures from experiments, the changes in enthalpy and entropy in reaction are given by least square method, i.e., ΔHm^⊖ = (-25.2 ± 1.5) kJ·mol^-1 and ΔSm^⊖ (-58.4 ± 2.0) J·mol^-1·K^-1, respectively.