An experimental study on laser transmission welding of transparent glass and 6061 aluminium alloy by a millisecond pulsed 300 W Nd:YAG laser is reported. The test of breaking strength is conducted by a universal tensile test machine, and the glass fracture morphology and weld sectional microstructure are analyzed by scanning electron microscopy. The effect of multipass welding and weld spacing on weld seam morphology, breaking strength, and fracture morphology is studied. The results indicate that a good glass-to-aluminium joint can be obtained if a millisecond pulsed laser is used. The maximum breaking strength of weldments is 159.93 N. When the distance between the welding seams is 0.8 mm, the aluminium alloy and glass can obtain good sealing.