Herein,a joint with quality of excellent grade was obtained based on an optimal laser-metal active gas arc welding (MAG) hybrid-welding process for SUS301L-HT stainless steel. The microstructure characteristics of the welded joint were analyzed through optical microscopy. The analysis showed that the weld exhibited the most serious softening, and its microstructure comprised columnar austenite grains and ferrite. The heat affected zone (HAZ) exhibited different degrees of recovery and recrystallization, and its hardness was higher than that in the weld. The crack growth testing was conducted in the weak area of joint strength (weld) to study the crack propagation characteristics and fracture feature at different stages and to discuss the impact of the weld microstructure on the crack growth process. Results indicated that ferrite was usually the initiation site of fatigue cracks and the preferred crack propagation channel. Resistance to crack propagation in the fusion zone can be improved through further process optimization.