Laser welding technology was adopted to weld Zr-base bulk amorphous alloy (BAA) Zr45Cu48Al7 (at.-%) plate. The structure of joint under different technical parameters during laser welding was researched, and the crystallization behavior of the bead and heat-affected zone (HAZ) during the thermal cycle of welding was primarily discussed. The results showed that an excellent joint has been obtained and there was no visible defect, pore or crack in both the bead and HAZ when the output power of laser-beam was 1200 W and the scanning velocity was 8 m/min. No crystal was observed in both the bead and HAZ with keeping the amorphous structure. However, crystallization occurred in both the bead and HAZ under the condition of the same output power but the scanning velocity of 2, 4 m/min. From the optical microscope and the micro-focused X-ray diffraction (XRD) experiment, it made sure that there was crystal in both the bead and HAZ under the scanning velocity of 2 m/min and the crystalline phases were mainly ZrCu phase and Zr38Cu36Al26 phase (τ5). There was some crystal in HAZ while no crystal in the bead under the scanning velocity of 4 m/min, and the crystalline phases were almost the same as under 2 m/min scanning.