At present, objects dictionary (OD) and object descriptions used in fieldbus intelligent instruments are based on variable-sized storage and constant property values, which constrains the flexibility and portability in data access and modularization and encapsulation in system design. In this paper, a kind of universal data structure for object description in OD was presented. Universal management of object description with different types could be realized with the proposed structure. Based on principle and methodology of Object-Oriented Design (OOD), an improved model for object description was proposed. In the improved model, constant value used in object code field of object description is replaced by function pointer pointing to object instance handler for data process of object instances belonging to the same class. Universal function structure is used for all class object instance handlers for different classes but instances belonging to different classes are manipulated differently with their own handlers. The improved model for OD and object description was proven effective and efficient by the practice of development and design of intelligent instruments in distributed control network.