The belt conveyor is an important material-transport equipment in metallurgy, mining, ports and thermal power plants, etc. It has an important engineering significance on the belt conveyor design, management and statistics. Based on the concept of three-dimensional digital design, this paper proposes a method of adding engineering attributes to the belt conveyor parts by extension dictionary of ObjectARX in 3D modeling system of the belt conveyor. By reading the attributes of parts, it is convenient and rapid to query the engineering information of single parts and manage all of the belt conveyor parts.