To improve the accruacy of field hyperspectral simulation and build the field spectral mixture model, the experiments for detecting mixture spectra of different detected angles and different ratios of leaf cover area were conducted to obtain the mixture spectra by using ASD FieldSpec3 Hi-Res field spectrum instrument with the reflex platform. Based on the theory of equidistant/homalographic model, the computation of weight coefficients for the model was expanded to calculation of three-dimensional weight coefficients. Taking account of the impact of zenith angle on weight coefficient, the three dimensional coefficient model was proposed for simulating mixture spectra, and comparing with the measured spectra for analysis. The results showed that the three dimensional coefficient model had more accurate computation of weight coefficient and had smaller error compared to equidistant/homalographic model. Especially for inclined detected angle, it had better simulation that it reduced the error 0.016 1 in RMSE and 0.07 in SAD. The three dimensional coefficient model considered the influence of detected angle, thus enhancing the estimation of mixture spectra and providing a new method for building field mixture model and unmixing mixed spectra from satellite data.