To investigate the solidification structure and inclusion behavior during the vacuum arc remelting process of ultra-large die-casting die steel， and to explore and study the process parameters of vacuum arc remelting， computer numerical simulation technology was employed to investigate the evolution of the molten pool shape during the smelting process of ultra-large die-casting die steel ingots （diameter 1 250 mm） under three different melting rates. The segregation patterns of elements were analyzed， and the relationship between melting rate and inclusion removal trajectory， as well as the effect of different helium pressures on the solidification quality of the ingots， were studied. The results showed that， during steady-state melting， the growth rate of molten pool depth was directly proportional to the melting rate. When remelting at melting rates of 12.50 kg/min， 13.65 kg/min， and 15.00 kg/min， the simulated increasing rates of molten pool depth were 0.257 mm/min， 0.307 mm/min， and 0.397 mm/min， respectively. The inclusion removal trajectories were reasonable at all three melting rates. When the melting rate was set at 12.50 kg/min and 13.65 kg/min， the solidification front of the molten pool could not reach or fully reach the edge of the crystallizer， posing a higher risk of subsurface inclusions on the lower surface of the ingot. The water cooling effect at the bottom of the crystallizer was extremely strong during the initial stage of remelting， resulting in a high cooling rate. Simulation calculations showed that C， V， Cr， and Mo all exhibited negative segregation to varying degrees at the three melting rates， with C and V being the most pronounced， followed by Mo， and Cr showing relatively less segregation. When the ingot height reached 500 mm， the negative segregation of Cr and Mo was essentially eliminated， and the negative segregation trend of C and V significantly weakened. Computational simulations studied the effect of helium cooling on the depth of the two-phase region at two melting rates. The introduction of helium significantly reduced the depth of the two-phase region， reducing the depth by over 40%. Within a certain range， the pressure of the introduced helium was inversely proportional to the depth of the molten pool's two-phase region. The introduction of helium significantly reduced the segregation effects of various alloying elements in the top region of the ingot， with the shape of the severely segregated elements zone changing from conical to flatter. The concentration distribution of elements became more uniform. Elements in the core of the ingot tended to show positive segregation， while elements on the surface of the ingot tended to show negative segregation.