A method for detecting multiple touch positions on a touch surface, which is applicable to a touch apparatus having multiple optical sensing modules, where each optical sensing module includes at least two optical sensing devices. The method includes: acquiring multiple pieces of sense information; determining multiple touch ranges for each piece of sense information; determining multiple points of intersection; selecting one of the pieces of sense information of which the touch ranges are used to calculate a greatest numbers of the points of intersection; for each touch range of the selected sense information, repeatedly selecting two of the points of intersection calculated using the corresponding touch range according to distances until the selected two points of intersection are verified as being located within the touch ranges of at least another one piece of sense information other than the selected sense information; and calculating the touch positions as actual touch positions according to the selected points of intersection when the selected points of intersection are verified as being located within the touch ranges of the at least another one piece of sense information other than the selected sense information.