The Dy-Al-Ti ternary alloys were melted in a vacuum arc furnace and then were annealed in a vacuum tube. By means of X-ray powder diffraction with the aid of differential thermal analysis and metallographic microstructure analysis, the test sample was characterized and the phase relationship in the Dy-Al-Ti ternary system at 600 ℃ was investigated. Then the boundary of two-phase regions and three-phase regions of islthermal section of Dy-Al-Ti ternary system and its solid solution degree were determined at 600 ℃. The isothermal section phase diagram of Dy-Al-Ti ternary system was structured. The results show that this ternary system at 600 ℃ contains 14 single-phase regions, 27 two-phase regions and 14 three-phase regions. Two ternary compounds Ti4Al43Dy and Ti2Al20Dy are confirmed in this system at 600 ℃.