To explore a suitable epitaxial laser metal forming(E LMF)process for depositing nickel based single crystal superalloy blocks,we selected suitable laser power,scanning speed,and cooling methods to form nine sets of experiments on the basis of previous experiments.We obtained a suitable process combination and studied the evolution and formation mechanism of the microstructure.The results showed that:proper heat input and cooling methods can achieve crack free continuous epitaxial growth；excessive cooling rate will lead to excessive thermal stress and thus induce cracks；the main regions are epitaxial growth regions,and there are non epitaxial growth regions at the surface and both ends.