Preparation method of antistatic spandex and prepared antistatic spandex

The invention provides a preparation method of antistatic spandex and the prepared antistatic spandex, and the preparation method comprises the following steps: (1) adding N-alkyl diethanol amine containing a tertiary nitrogen group into PTMG (polytetramethylene glycol), and then mixing with a diisocyanate compound to obtain an isocyanate-terminated prepolymer; (2) after the prepolymerization reaction is completed, DMAc with the acid value of 200 ppm to 3000 ppm is used for dissolution; (3) adding a chain extender and a terminator into the pre-polymerized solution to carry out chain extension reaction, and adding an additive to obtain a spandex spinning stock solution; and (4) carrying out dry spinning to obtain the antistatic spandex. N-alkyl diethanol amine containing a tertiary nitrogen group is introduced into a diol raw material of the spandex, DMAc with a specific acid value is used for dissolving a prepolymer after a prepolymerization reaction, acetic acid in DMAc reacts with the tertiary nitrogen grou