Zincalume steel ( G550 ) is commonly used in various construction fields because of its high corrosion resistance and good mechanical properties. In recent years, a number of steel companies have massively produced zincalume steel ( G550 ) with large volumes of waste. For the reduction of massive industrial wastes, the zincalume steel ( G550 ) was welded in the lap joint configuration using different welding parameters in the metal inert gas ( MIG) welding and laser beam welding ( LBW) process in this study. The MIG welding and LBW are more welcomed welding methods due to their high efficiency and low cost. However, they are different as the LBW offers welding speed three to five times faster than MIG welding, while LBW\' s heat transfer to workpieces is much less than MIG welding, which can avoid some distortions. The microstructure of zincalume steel ( G550 ) was investigated using scanning electron microscopy ( SEM ) and the microstructure characterizations of welded specimens were analyzed. The experiment found the columnar dendrites extended under the heat flow direction during the MIG welding and LBW process. Thus, the columnar grains were formed in between the equiaxed zone and fusion zone ( FZ) at high heat input and slow cooling rate. Moreover, the grain size of FZ was comparatively smaller than heat affected zone ( HAZ) and base metal ( BM) .