Photomask black defect repairing method

The embodiment of the invention provides a photomask black defect repairing method. The method comprises the following steps: determining a to-be-repaired area completely containing black defects on a to-be-repaired photomask and position coordinates of the to-be-repaired area in the to-be-repaired photomask; intercepting a local reference pattern corresponding to the to-be-repaired area from an original design pattern of the to-be-repaired photomask according to the position coordinates, converting the local reference pattern into an available pattern which can be identified by a photoetching machine, and importing the available pattern into the photoetching machine; sequentially carrying out cleaning and photoresist coating treatment on a photomask to be repaired, and then putting the photomask into a photoetching machine; controlling the photoetching machine to determine a to-be-repaired area on the to-be-repaired photomask according to a pre-input position coordinate, and performing fixed-point local expo