Abstract: This paper summarizes the development from digital mock-up to digital twin, thus clearly clarifyingthe connotation of digital twin from prospective of digital product definition. Firstly, taking the relevantpractices in Airbus as example, the evolution of the digital mock-up’s connotation is introduced, by whichthe essence of digital product definition can be illustrated. Secondly, based on the state of the art of digitaltwin, the definition and purpose of digital twin concept are fully elaborated, accompanied by the thoroughdifferentiation analysis between digital twin and cyper-physical system as well as the augmentation for digitaltwin and digital product definition’s relationship. Finally, the key support techniques for fulfilling thedigital twin concept are deduced.