The invention discloses a light curtain fault detection method and system. The method comprises the following steps that when an elevator reaches the current target floor, and a door is opened, if the conditions that a light curtain of the elevator is shielded by a shielding object, and the resetting is not performed in the preset reset time are detected, whether the elevator generates forced door closing or not is detected; if the forced door closing occurs, the continuous action time of the light curtain corresponding to the current target floor is obtained, wherein the continuous action time is from the time of detecting the light curtain shielded by the shielding object to the time of the forced door closing occurrence of the elevator; the light curtain is subjected to fault detection according to the continuous action time. The light curtain abnormality can be actively detected, so that the maintenance personnel can discover the abnormality in time and can deal with the abnormality; the reliability of an elevator system is improved.