1. A smoke detecting method, comprising: capturing a plurality of images; determining one of the plurality of images as an analyzable image when the one of the plurality of images is identified to have a moving object; analyzing a chrominance variation of the analyzable image; analyzing at least one of an edge blur and a flickering frequency of the analyzable image; comparing at least one of analyzed results from the analyzing steps with a corresponding predetermined feature; and determining the moving object is a smoke when at least one of the analyzed results conforms to the corresponding predetermined feature.