For developing a new aluminum brazing flux, the liquidus in the pseudo-ternary system KAlF4-K3AlF6-KBe2F5 were determined by DTA and visual poly-thermal methods. The results indicated that the ternary eutectic point E in the system melts at 310 degreesC and located in KBe2F5 (81 mol%), KAIF(4) (15 mol%) and KF (4 mol%). The melts those contain KBe2F5 over 70 mol% will present glassiness during cooling.