As the main object manipulated by a software system, data with a domain standard can contribute to the process of software design and data shareware between software systems. In this paper, focusing on domain data standardization, a domain data modelling language (DDML) and a domain data modelling method (DDMM based on the type theory are proposed. In DDML, the syntax and semantics of types and terms are defined to describe the structure of the domain data types and objects, and the typing rules are defined to process the judgement of t:T. For DDMM, the data modelling processes are presented with the data modelling of κ₁ (atomic type), κ₂ (data element), κ₃ (data element directory) and the generation of typing rules in κ₃. Furthermore, the definition of the data element directory sequences and the algorithms of checking its correctness are defined. Finally, a prototype of the domain data modelling system as a modelling tool is developed and applied to a real case of large scale by the generation of the domain data standard and its evaluation.