Abstract: CsF-AlF₃ flux and KF-AmF₃ fluxes were selected, the effects of removing the oxides on the surface of 6063 aluminum alloy by these two fluxes were studied at different temperatures, and then the reaction mechanism between flux and surface oxide film of 6063 aluminum alloy was analyzed and discussed.It is discoved that the oxide film on the surface of 6063 aluminum alloy was removed by CsF-AlF₃ flux in a reacting and/or dissoluting way, and the HF formed at high temperature from NH4F was the critical compounds existed in the CsF-AlF₃ flux.In addition, the formation of HF was improved and accelerated duo to the H₂O, hence the process of removing the oxides was accelerated by the flux.The CsF and AlF₃ were not found, and only a few amount of CsAlF₄ was found in the residuai of CsF-AlF₃ flux, and also, the main residua of KF-AlF₃ flux was KAlF₄ at the 570℃, KAlF₄ was not found at the 610℃, which only a few amount of KMgF₃ was found.Results also indicated that in the residua of KF-AlF₃ flux, Mg, Mn and KAlF₄ would loss gradually, which lead to the melting point of flux increasing rapidly and the flux fluidity became poorer.