A method and system of preventing a loss/theft of a surveillance target including a mobile device using a wireless personal area network (PAN) or a wireless local area network (LAN) which can receive, from the mobile device included in the surveillance target via a gateway, location information of the surveillance target generated by using mobile device information for the surveillance target, the mobile device information being collected by a sensor of the mobile device, and signal information communicated between the mobile device and a fixed device, can determine whether there is a loss or theft by comparing surveillance target information and a permission standard, and can provide alert information including the location information of the surveillance target when the loss or theft occurs.