Disclosed is an object determining system comprising an optical sensor, a kind determining circuit and an element analyzing circuit. The optical sensor comprises a kind determining region and an element analyzing region, wherein the optical sensor captures at least one object image of an object via the kind determining region, and acquires element analyzing optical data via the element analyzing region. The kind determining circuit is configured to determine an object kind of the object according to the object image. The element analyzing circuit is configured to analyze element of the object according to the element analyzing optical data and the object kind. An object determining system applying tow stage object sensing steps to determine an object kind is also disclosed.