Context : The spectral predictions of stellar population models are not as accurate in the ultra-violet ( UV ) as in the optical wavelength domain . One of the reasons is the lack of high-quality stellar libraries . The New Generation Stellar Library ( NGSL ) , recently released , represents a significant step towards the improvement of this situation . Aims : To prepare NGSL for population synthesis , we determined the atmospheric parameters of its stars , we assessed the precision of the wavelength calibration and characterised its intrinsic resolution . We also measured the Galactic extinction for each of the NGSL stars . Methods : For our analyses we used ULySS , a full spectrum fitting package , fitting the NGSL spectra against the MILES interpolator . Results : We find that the wavelength calibration is precise up to 0.1 px , after correcting a systematic effect in the optical range . The spectral resolution varies from 3 Å in the UV to 10 Å in the near-infrared ( NIR ) , corresponding to a roughly constant reciprocal resolution R = \lambda / \delta \lambda \approx 1000 and an instrumental velocity dispersion \sigma _ { ins } \approx 130 km s ^ { -1 } . We derived the atmospheric parameters homogeneously . The precision for the FGK stars is 42 K , 0.24 and 0.09 dex for T _ { eff } , log g and [ Fe/H ] , respectively . The corresponding mean errors are 29 K , 0.50 and 0.48 dex for the M stars , and for the OBA stars they are 4.5 percent , 0.44 and 0.18 dex . The comparison with the literature shows that our results are not biased . Conclusions :