Near infrared spectroscopy was applied to rapidly predict microfibril angle (MFA) and fiber length of Neosinocalamus affinis Keng by using a fiber-optic probe in diffuse reflectance mode. The MFA and fiber length were measured by X-ray diffractometry and optical microscope, respectively. Partial least squares (PLS) was used to build models based on raw and pretreated spectra, including noise spectra and noise combined with orthogonal signal correction (OSC) spectra. The results showed that the PLS models of MFA and fiber length, based on noise combined with OSC spectra, gave the strongest correlations, with correlation coefficient (R) of 0.893 6 and 0.988 3 and root mean standard error of prediction (RMSEP) of 0.292 0 and 0.146 0 in prediction set. The correlations between NIR predicted and MFA/fiber length actual values are very good. Therefore, it is concluded that MFA and fiber length of N. affinis can be estimated by NIR spectroscopy with sufficient accuracy.