This invention provides an electric spark processing method for sealing grooves of an aero engine guide vane. The method comprises the following steps: (1) two copper-tungsten alloy blocks are fixed on an electrode pedestal and are processed into two electrodes by adopting a milling mode, wherein the two electrodes have the shapes same as and the positions matching with those of the sealing grooves, formed in large and small margin plates of the guide vane, to be processed respectively; and (2) the two electrodes are placed aligning to the parts, to be processed, of big and small margin plates of the guide vane respectively, an electric spark processing machine is started to ensure that the two electrodes carries out electric spark processing on the parts to be processed in the depth direction of the sealing grooves; the two electrodes are aligned to a next part to be processed after processing of the sealing groove of the processed surface is finished, and processing continues according to the process conditions until all the sealing grooves, in the same type, formed in the guide vane are processed; and after the electrodes wears, the two copper-tungsten alloy blocks which are fixed on the electrode pedestal are reprocessed into electrodes by using the milling mode, and then the sealing grooves are continuously processed.