The invention discloses a parallel groove clamp lap-joint device, which comprises a clamp fixing device, a lead locking device and a pressure cylinder fixing device, wherein the clamp fixing device comprises a first clamp fixing block, a second clamp fixing block arranged at the lower side of the first clamp fixing block, a guide connecting rod connecting the first clamp fixing block and the second clamp fixing block and a clamp fixing device control structure which enables the first clamp fixing block and the second clamp fixing block to clamp or loosen a parallel groove clamp, the second clamp fixing block is provided with a lead pass-through slot provided for a lead to transversely pass through, the lead locking device comprises a locking block arranged in the lead pass-through slot anda lead locking device control structure which controls the locking block to move so as to lock or loosen the lead, and the pressure cylinder fixing device comprises a pressure cylinder fixing block connected with the second clamp fixing block and pressure cylinder clamping pieces arranged at the left and right sides of the pressure cylinder fixing block respectively. The parallel groove clamp lap-joint device can be operated by one person, and can complete lap joint through one set of tools, thereby greatly improving the lap-joint efficiency of the parallel groove clamp.