Abstract: The heterogeneous wavelength hybrid laser welding (HW-HLW) technology effectively integrates the advantages of different laser beams as independent welding heat sources. It exhibits considerable potential for application in laser processing, particularly in the joining of metals that are inherently challenging to weld with conventional light sources. In this paper, the HW-HLW experiment was carried out for 2195 Al-Li alloy. The microstructure of welded joints under different laser heat sources was investigated. The thermal-flow coupling model during welding was established to elucidate the effect of molten pool flow behavior on the microstructure distribution characterisitcs. The results indicate that, compared with that in single-fiber laser welding, the flow behavior of the molten pool promotes the increase in the waist region in the process of HW-HLW, and the ability of relatively cold mixed liquid containing crystal nuclei to enter the molten pool is enhanced. Consequently, a larger non-dendritic equiaxed zone (EQZ) is formed in the waist region of the weld, and the grain size of equiaxed fine crystals is significantly increased. Besides, the growth direction of columnar dendrites in the weld is roughly perpendicular to the EQZ boundary.