The effect of initial lamellar structure of β heat treated Ti-6Al-4V alloy on the globularization behavior during the multi-step forging was investigated. Specimens of different lamellar thicknesses were upsetted and stretched by side pressing repeatedly, i.e. multi-step forging, at the sub-transus temperature to break down the lamellar structure. The microstructural changes after multi-step forging were analyzed in the light of globularization behavior. The results showed that the thick lamellar structure was more difficult to be transformed to homogeneous equiaxed structure than thin lamellar structure.