Digital twin has been recognized as a new development stage of smart agriculture. By establishing physical systems and digital spaces for agricultural production, digital twin technology has achieved the integration of "connection - perception - decision - control", which can address the complexity of agricultural production systems through higher levels of intelligent control. The development of China's agricultural digital twin system is relatively late, and the overall research and technical equipment are in the exploratory and initial stage. In this article, on the basis of research on multidimensional information acquisition, data analysis, and production simulation models for dairy farming, a digital image of dairy farms in virtual space is established, which is targeting key production scenarios such as feeding management, breeding management, health management, and environmental regulation, and a digital twin system for dairy farming is constructed, implementing the data-driven, real-time feedback, simulation deduction, and intelligent control through virtual control of breeding technology processes and production equipment. And the digital twin system has been conducted specific application and preliminary verification on a 1000-herd scale dairy farm in Jiangsu Province.