Abstract: Provided is an automatic secondary degassing fixed-length mechanism for an ultrathin heat pipe. The automatic secondary degassing fixed-length mechanism comprises an automatic lifting device A installed on a length adjustment sliding table, an automatic clamping device B, a length positioning and extension device C and a PLC. The present invention, having the advantages of simple structure, high efficiency and stability, is suitable for the secondary degassing fixed-length processing of heat pipes of different lengths, and particularly suitable for processing ultrathin heat pipes made of a thin-walled heat pipe by a flattening process, having advanced structural design and stable and high-efficiency production. In this mechanism, size positioning and automatic clamping in the secondary degassing fixed-length process for the heat pipes are correspondingly achieved through the automatic lifting device A and the automatic clamping device B.