Abstract: Regarding the porosity defect in the melting welding of AlSi10MnMg die-cast aluminum alloy, a bubble nucleation and growth model was established based on thermodynamic and kinetic principles. The evolution behavior of bubbles induced by the difference in hydrogen solubility at the solid/liquid interface during the molten pool solidification stage was studied theoretically, and the control law of molten pool behavior on welding porosity was explored through laser welding experiments. The results show that the uneven distribution of hydrogen concentration in the molten pool leads to the precipitation of supersaturated hydrogen at the front of the solid/liquid interface, which is the fundamental cause of porosity. The formation of porosity is the result of the competition between the bubble floating speed and the advancing speed of the solid/liquid interface, and is directly affected by the dynamic behavior of the molten pool. In continuous laser welding, the welding speed is positively correlated with the number of porosities and negatively correlated with the porosity rate, which is attributed to the increased welding speed accelerating molten pool solidification and inhibiting bubble growth. The trend of the model's predicted values is consistent with the experimental values, and the gap narrows as the welding speed increases. In pulsed laser welding, the increase in pulse width causes a continuous rise in the porosity rate; the pulse frequency is the key control parameter, and the number of porosities decreases sharply and stabilizes at 60 Hz.