Crack is the common drawback in deposition manufacturing process with high energy beam, which usually leads to the manufacturing process being given up halfway. So it is important and urgent to investigate the generating principle of crack and establish relative means to prevent crack appearance. In this paper, the principle of crack generating in the process of hybrid plasma and laser manufacturing was studied experimentally and systematically. The influences of power system and shielding atmosphere on crack were researched. The results were summarized as follows: (1) The crack generating in the course of manufacturing is mainly heat crack. (2) Excessive energy density and temperature will result in crack. (3) The best method preventing part being manufactured from oxidation is to put the whole part into the inert gas.