Aiming at the problems of low quality consistency, difficult control of key tooling status and low comprehensive efficiency, this paper studies the intelligent quality management and control decision-making of final assembly workshop based on digital twin technology on the basis of assembly automatic production line. The overall architecture of the integrated application of a product assembly intelligent workshop based on digital twin is built, and the key technologies such as the quality consistency management and control technology of variable batch assembly and the life prediction technology of key tooling closely related to quality under complex working conditions are described. The error transfer model of product assembly process and the life twin model of key tooling in the whole life cycle are designed. The results show that the technology realizes the consistency control of production process quality and the life prediction of key tooling, forms a precise and intelligent control mode, and promotes the transformation of product assembly quality control from passive mode to autonomous intelligent control mode.