The invention relates to a tightly packaged fiber, and a dual-core cable using the tightly packaged fiber and a processing method thereof. The tightly packaged fiber consists of a single-mode or multi-mode fiber core, a cladding layer clad on the circumference of the fiber core, a primary coating layer coated on the circumference of the cladding layer and a secondary coated layer tightly sleeved on the circumference of the primary coating layer, wherein the secondary coated layer is a polyvinyl fluoride protection layer. By taking polyvinyl fluoride which has relatively high chemical corrosion resistance, creep resistance and compressive strength and relatively wide bearable temperature range as the secondary coated layer of the tightly packaged fiber, the tightly packaged fiber can have enough mechanical and environmental protection capability and can be independently used. The dual-core cable using the tightly packaged fiber, which is processed by the method has the advantages of small volume, light weight, stable performance and low cost, is suitable for indoor comprehensive wiring and can be used as internal connection wires of various optical devices, optical modules and optical distribution frames.