Wearable devices, which can be worn by humans and animals, have drawn great attentions in recent years. In the current systems, wearables and applications are closely bounded with each other, it is thus difficult to make the systems extensible and flexible. Therefore, we propose a novel wearable system, called Wear-I, which is consisted of multiple wearables and able to carry out various wearable services. However, because these multiple wearables are often heterogeneous and dynamic change during their usages, it is crucial to effectively manage these wearables. This research is to study the necessary device management functions that are categorized into three parts: device information management (DIM), device usage management (DUM), and device operation management (DOM). DIM is for managing device registrations, working states and using logs. DUM is to support retrievals of device information, invocations of necessary devices in an application, and knowledge bases about the device features and usages. DOM is to provide the management of device information database, an interface for a user to operate devices and database, and a set of APIs directly useable by various wearable applications. A series of periments have been conducted to present and test the proposed device management functions.