Magnesium alloy Nd: YAG pulse laser spot welding method

The invention discloses a magnesium alloy Nd: YAG pulse laser spot welding method which is characterized in that peak steep drop progressive slow cooling type pulse waveform is adopted to inhibit generation of laser welding spot air holes and solidification cracks, and the method comprises a peak stage, a rectangular main wave band, a steep drop wave band and a slow drop wave band; the peak power change interval of the peak wave band is 2 * p-p, and the pulse time is 0-1ms; the peak power of the rectangular main wave band is p, and the pulse time is 1ms-4ms; the peak power change interval of the steep drop wave band is p-n, n is greater than or equal to 0.1 p and less than or equal to 0.5 p, the pulse time is t, and t is greater than or equal to 1ms and less than or equal to 5ms; the peak power change interval of the slow descent wave band is n-0, and the pulse time is t. According to the method, generation of laser spot welding defects can be effectively inhibited, the laser spot welding absorptivity is impr