Method of detecting subject of image and imaging device thereof

A method of detecting subject of image, comprising the follow steps of:

• providing an image capturing module to capture a temporal image;
• providing an image processing module to receive the temporal image and decide a plurality of objects from the temporal image;
• using the image processing module to define a plurality of regions on the temporal image based on a center of the temporal image;
• using the image processing module to assign an initial setup value to each of the objects according to the region corresponding to each of the objects;
• using the image processing module to execute an operation to each of the objects to increase or decrease each of the initial setup values;
• using the image processing module to execute a sorting based on each of the initial setup values which have already modified by the operation;
• and
• selecting at least one of the objects as a subject of the temporal image based on each of the initial setup values after the sorting.