The invention relates to a near-infrared spectral detection method for the residual content of a solvent N,N'-dimethylacetamide (DMAC) in polyurethane elastic fiber filaments. The method comprises the following steps: (1) preparing a series of acetone and DMAC solutions of different concentrations, and selecting a sufficient amount of representative calibration set samples; (2) determining a near-infrared spectral spectrogram of the calibration set samples, carrying out spectral pretreatment on a wave band, of 12,000-4,000cm<-1>, of the spectrogram, and then, establishing calibration models by adopting a partial least square method; (3) carrying out extracting pretreatment on the polyurethane elastic fiber filaments, then, determining a near-infrared spectral spectrogram of an extract, treating the wave band, of 12,000-4000cm<-1>, of the obtained spectrogram by adopting the same pretreatment method as in the step (2), and analyzing the pretreated spectrum by adopting the corresponding calibration model obtained in the step (2), thereby obtaining the content of DMAC in a polyurethane elastic fiber filament sample to be detected. The method has the advantages that the analysis process is simple and rapid, the interference resistance is strong, the analysis is non-destructive, the sampling quantity is small, and the like.