Laser-induced crystallization in the initialization and erasing processes of a AgInSbTe phase-change optical recording disk was studied. After laser initialization, a AgInSbTe film formed a metastable face-centered cubic (f.c.c.) phase. Both the high-resolution transmission electron microscopy (HRTEM) cross-sectional image and the static test results showed the difficulty of nucleation. At low linear velocities, i.e., CD 1X and CD 2X, several clusters formed in amorphous marks due to the low cooling rate and the longer reheating of the subsequently applied pulses. These clusters enhanced nucleation and the amorphous marks probably crystallized via the nucleation and grain growth mechanism in the erasing process. The degree of order in the amorphous marks decreased with linear velocity, and no clusters existed in the amorphous marks at CD 4X. Due to the difficulty of nucleation, the erasing process was predominated by the direct grain growth mechanism at high linear velocities.