A line spring jack and an assembling method are disclosed. The line spring jack comprises a jack body, a jack cap, a line spring wire and a positioning plug. Said jack body further comprises a plug hole; said line spring wire is located in said plug hole; said jack cap is connected to one end of said jack body; said jack cap further comprises a through hole connected to said plug hole; one end of line spring wire is clipped in a space formed between said jack cap and said jack body; wherein said plug hole further comprises a groove in the bottom; the caliber of the groove is smaller than the diameter of said plug hole; said positioning plug includes a part in the groove and a part in the plug hole, the part in the groove is tightly matched to said groove.