A rapid quantification of oxytetracycline hydrochloride in cattle premix using Attenuated total reflection-Fourier-transform infrared spectroscopy (ATR-FTIR) combined with partial least squares (PLS) was performed. Rapid quantification of the prohibited component of oxytetracycline hydrochloride in cattle premix was carried out. 98.00% (W/W) oxytetracycline hydrochloride was added to the blank cattle premix, and 113 mixed samples were prepared with oxytetracycline hydrochloride concentrations ranging from 0.00% to 5.00%. Pure water was used as the extractant, and the extract was dried by an infrared lamp and used for IR spectroscopy. Three pretreatment methods were employed: Savitzky-Golay convolution smoothing (S-G), standard normal variation (SNV), multivariate scattering correction (MSC), and three variable selection algorithms: Interval partial least-squares (iPLS), Moving partial window least-squares (MWPLS), the bootstrapping soft shrinkage (BOSS). Among them, SNV combined with the BOSS algorithm obtained the best model results: RMSECV=0.337 0, R2CV=0.946 9, RMSEP=0.317 3, R2pre=0.934 6. The model predicted 29 samples with contents ranging from 0.53% to 4.67%, and the average relative error of prediction was 0.126 7. Meanwhile, the variables selected by the BOSS algorithm were mainly concentrated in the absorption regions of the characteristic peaks of oxytetracycline hydrochloride (1 674~1 593 and 1 175~1 017 cm-1), which can provide a valuable reference for the ATR-FTIR technique in the rapid detection of oxytetracycline hydrochloride in feed.