Spinning and finishing techniques of a durable softening and water-repellent PP/HDPE heat-bondable fiber were introduced. The fiber has a core-sheath structure. PP is the core and HDPE is the sheath. The core-sheath fiber structure and spinning materials properties make the fiber have a good heat-bonding performance. During the finishing process the fiber got a durable softening and water-repellent quality by the durable waterproofing agent—a mixture of PMHS and PDMS. Experiments show that the fibers begin to melt and bond each other at 127.5°C and could keep a good water-repellent performance after being washed five circles.