Method for testing content of residual dimethyl sulfoxide in polyacrylonitrile precursor

The invention discloses a method for testing the content of residual dimethyl sulfoxide in a polyacrylonitrile precursor, which comprises the following steps of (1) mixing and oscillating the polyacrylonitrile precursor and acetone at 30-50 DEG C, so that the residual dimethyl sulfoxide in the polyacrylonitrile precursor is leached into the acetone, and (2) taking acetone as a reference solution,testing the acetone solution containing dimethyl sulfoxide obtained in the step (1) by using an ultraviolet spectrophotometer, and calculating the content of residual dimethyl sulfoxide in the polyacrylonitrile precursor. According to the method, acetone is adopted as an extracting agent of dimethyl sulfoxide in polyacrylonitrile precursor, dimethyl sulfoxide in the precursor can be leached at a low temperature, decomposition of dimethyl sulfoxide is avoided, acetone has better wettability to PAN fibers than water, the extraction efficiency is higher, meanwhile, ultraviolet absorption of dimethyl sulfoxide in acetone