In order to detect soluble solids content(SSC) in fruit conveniently and rapidly, a portable soluble solids content spectrometer for apple was designed based on STS spectrometer. The NIR spectral data were obtained by the portable fruit soluble solids content spectrometer and recorded with the integration time of 100 ms in the wavelength range of 630~1 125 nm. Meanwhile, two structural parameters light source angle α and distance between light source and probe W were analyzed for investigating the influence of the response properties of visible-NIR spectra. The partial least square regression model and least squares support vector machine model were established. By comparison, partial least square regression model performed better. When the distance between probe and light source was 15 mm and the angle of light source was 45, its performance was the best with the root mean square error(RMSEP) of prediction set of 0.334% and correlation coefficient of prediction set of 0.924.