Liquid film migration (LFM) in the fiber laser welded Inconel 617 joint was investigated. The results show that the LFM occurs in HAZ of the laser welded Inconel 617 joint. The element of Mo in the migrated region is slightly richer than that in the adjacent matrix. The diffusional coherency strain due to the lattice mismatch between the element of Mo and the matrix atom is the dominant factor contributing to the occurrence of LFM in HAZ of laser welded Inconel 617. The migration of the liquid film is promoted by the thin initial liquid film and the slow cooling rate in large heat input. LFM tends to occur on the grain boundary (GB) with the fine particles and the GB-resolidified particles are formed on the GB with the large particles. Liquation cracking is reduced in the welds with the high heat input and in the solution treatment condition by LFM (1100 °C/1 h).