A detection system for detecting appearances of many electronic elements includes a rotary module, a feeding module and a detection module. The rotary module has a base structure and a hollow transparent rotary structure disposed on the base structure. The feeding module is disposed beside one side of the hollow transparent rotary structure in order to sequentially guide the electronic elements to the top surface of the hollow transparent rotary structure. The detection module has a plurality of detection units sequentially disposed around the hollow transparent rotary structure. Each detection unit is composed of an image-sensing element for sensing the electronic elements, an image-capturing element for capturing surface images of the electronic elements and a classifying element for classifying the electronic elements.