The invention provides a locating method for a cross wire in radiotherapy equipment. The locating method comprises the following steps: when a rotating frame of radiotherapy equipment is at a first frame angle, rotating a treatment head about the longitudinal axis of the treatment head to make the treatment head reach at least three predetermined positions, wherein a cross wire is installed on the ray path in the treatment head; at each predetermined position, acquiring a projected image corresponding to the cross wire irradiated by rays through an image acquisition element; and determining the deviation of the actual position of the cross wire relative to the ideal position thereof at the first frame angle according to the projection of the center of the cross wire in each projected image and any of the multiple projected images. According to the scheme, the position of the cross wire is located by ray projection, the accuracy is higher, and the operation is more convenient.