In order to reveal the evolution of composition and microstructure of GH4169 alloy during the homogenization treatment, the alloy microstructure during heat treatment were in-situ observed by high temperature metallographic microscope. The particle size distribution of Laves phase in the alloy after cooling was analyzed by quantitative metallographic analysis. The distribution characteristics of Nb element in alloy before and after heat treatment were analyzed by EPMA. When the heating temperature of GH4169 alloy rises about 1151 ℃, the initial melting happens around the Laves phase. The particle number of Laves phase in GH4169 alloy increased after heat treatment, the particle size of maximum Laves phase decreased significantly, and the proportion of small Laves phase in alloy increased slightly. At 1180 ℃, there was a certain amount of liquid phase existing in GH4169 alloy, but the NbC phase undissolved. After heat treatment, the segregation of Nb element in the black area between the primary dendrites still existed, but the distribution of Nb element in the γ phase dendrite became more uniform.