In this paper, we studied the relationship between the morphological development of the solid-liquid interface and the needle-like stress zones in Czochralskimethod-grown YAG single crystals doped with Nd. The experimental results established that the needle-like stress zones were originated from the solute (Nd) -rich zones due to constitutional supercooling. By studying the needle-like stress zones with photo-elasticity method, the stress in these zones was found to be axially symmetrical comperssive. We have also studied dislocation arrays along the boundaries of solute (Nd)-rich zones by means of etching method and birefringence observation, and measured the dis location density. The measured density agrees roughly with the value estimated according to the theory of misfit dislocations.