First attempt to predicting physical properties of paper by Near Infrared Spectroscopy (abbreviated as NIRS) mathematical model, Acacia is a kind of fast-growing tree which is a potential resource in pulp and paper industry. The mathematical models of physical properties of Acacia unbleached kraft paper were established by software OPUS6.5 of Near Infrared Spectroscopy. Spectral data of Acacia unbleached kraft paper were acquired by Near-Infrared. Physical properties, which include quality, whiteness, tensile index, burst index and tear index, of the paper were measured by GB methods. NIRS mathematical models between the spectral data and the laboratory reference values were established and optimized by software OPUS6.5 partial least squares (abbreviated as PLS). The NIRS mathematical models were evaluated by its parameters, and used to predict the physical properties of unknown samples rapidly and accurately. Compared with NIRS mathematical model of physical properties of Acacia unbleached kraft pulp, the NIRS mathematical models of paper have a better prediction on unknown samples; Compared with traditional laboratory methods, predicting properties of paper by the NIRS mathematical models of paper is rapid, accurate and non-destructive.