The invention relates to a radiation leaky cable outer conductor longitudinal package mold and a longitudinal package forming method. The longitudinal package mold comprises a mold body. The mold body comprises a trumpet-shaped cloth bag tube which is formed by winding double-layer cloth and a fixing part which is used for fixing the cloth bag tube. The cloth bag tube comprises a first passage which is formed between the double-layer cloth and a wound second passage. An outer conductor passes through the first passage. A cable core passes through the second passage. The longitudinal package forming method provided by the invention comprises the steps that the longitudinal package mold enables the belt-like outer conductor and the cable core to run into the entrance of the first passage and the second passage through continuous application of traction force; the outer conductor and the cable core walk in the first passage and the second passage and run out of the exit; when the belt-like outer conductor walks in the first channel, the belt-like outer conductor gradually forms a cylinder with the cloth bag tube; and the cylindrical outer conductor at the exit wraps the cable core. According to the longitudinal package mold and the method, the slot hole of the outer conductor is not easily deformed.