It’s extremely strict on crack of nuclear power plant containment for the durability and barrier to nuclear leakage. High concrete strength and large heat of hydration make it difficult to control construction cracks. At the foreign and domestic nuclear power plants delamination or subregion had been adopted normally for mass concrete construction, but still more cracks appeared, and had paid great costs to deal with them. Based on theoretical analysis, in the article the study on merge concreting and crack control technical of base slab of the current popular CPR1000 nuclear power plant containment is carried out. Through the analysis of thermal stress laws on the placement of the different thickness, different sliding ability, different curing methods and construction capabilities and influences of other installation and construction process under the merge concreting, the paper puts forward and validates the feasibility of the merge concreting, and propose many crack-prevention measures from the design, construction, monitoring of temperature stress and shrinkage and others. Finally, the merge concreting has been successfully applied, breaking the routine and having been achieved remarkable economic and social benefits.