The invention relates to the technical field of non-traditional machining, in particular to an electric spark block-by-block machining method for a diffuse type air film cooling hole. The method comprises the following steps that an area to be machined is divided into a plurality of subareas according to the shape and size of a diffuse type outlet of the air film cooling hole to be machined; a slender type electrode is used for carrying out electric spark machining, one subarea is machined after one-time feeding of the electrode, and the complete diffuse type outlet of the air film cooling hole to be machined is machined after several times of feeding. According to the electric spark block-by-block machining method for the diffuse type air film cooling hole, the block-by-block machining technology is adopted, the area to be machined is divided into the multiple subareas to be machined respectively, accordingly, the common slender type electrode can be adopted for machining the diffuse type outlet of the air film cooling hole, the electrode is easy to repair after machining is finished, the machining efficiency of the air film cooling hole is effectively improved, and the machining cost is greatly reduced.