An optical touch system is provided. A reflector is disposed beside a base plane. At least one light source is disposed beside the base plane and provides a detecting light, wherein the detecting light is transmitted to the reflector. At least one optical detecting sensor is disposed beside the base plane. A processor is coupled to the optical detecting sensor, wherein when a first object and a second object approach or touch the base plane, the processor determines which one of the intensity of a first portion of a signal corresponding to the first object OB1 and the intensity of a second portion of the signal corresponding to the second object OB2 from the optical detecting sensor is larger. Additionally, a method of touch detection and a computer program product are also provided.