GH3625 superalloy is a type of solid-solution strengthened nickel-based wrought superalloy having Mo and Nb as the main strengthening elements. Because of its excellent high-temperature mechanical properties and oxidation resistance below 650 ^oC, it can be used in harsh stress and atmosphere environments. It is mainly used as a pipe material for aeroengine fuel main pipe, nuclear power steam generator heat transfer pipe, and pressure pipe, etc. Owing to the high alloying degree of nickel-based superalloys, large deformation resistance, and narrow thermal processing temperature range, the pipe preparation process is complicated. In this study, the as-cast and homogenized pipe billets were used for a short-flow hot extrusion pipe preparation test using the same process. The homogenized pipe billet was extruded successfully, and the pipe burst occurred during the extrusion of the as-cast billet. The pipe burst behavior was studied by OM, SEM, and EBSD, with an EDS analysis. The results showed a considerable amount of Laves phases in the as-cast pipe billet, and the Laves phases and micro-segregation were essentially eliminated after homogenization. Adiabatic heating of the as-cast pipe billet leads to the Laves phase remelting during the hot extrusion process, which is the main reason for pipe bursting during a hot extrusion process. The cracking mode of the pipe burst is a quasi-cleavage fracture, combining brittle fracture and ductile fracture with the predominance of the brittle fracture.