A method for predicting user's intent is provided. The method is performed by a computing device and includes: receiving spatial information and acceleration data from a portable device and a wearable device worn by a user, wherein the wearable device and the portable device measure the spatial information between each other via UWB when either the wearable device or the portable device detects that an activity of the user or a motion status of either the wearable device or the portable device has changed based on the acceleration data measured by accelerometers in the wearable device and the portable device; identifying a behavior of the user using the wearable device and the portable device and predicting user's intent based on the spatial information and the acceleration data; and transmitting a notification signal to the wearable device to notify the user of user's intent.