The invention provides a manufacturing process of a rubber sole free of flash. The manufacturing process has the advantages that flash are reduced and manual trimming is avoided, and comprises the following steps of carrying out mixing, carrying out pressing to form a sheet, preheating a mold, pre-pressing the sheet, opening the mold for laminating, closing the mold for vulcanization and opening the mold for tearing off a film. The rubber sole manufactured through the process is free of flash. According to the process, the flash of the rubber sole is prevented from being generated, the attractiveness of the product is guaranteed, a large amount of sole materials are prevented from wasting, the process of trimming the flash is omitted, and the labor cost is reduced.