Rock spectrum research is the base of the remote sensing geology. It’s of great significance of exploring the relations between rock spectrum and other rock natures. In the present study, 36 fine crushed lava samples each measuring 5 cm×5 cm×5 cm were tested for its spectrums by SVC HR-768 portable spectrometer. But before measuring each sample, white boards should be calibrated and after measuring the curves of spectrum of each sample should make a 5 nm smooth resample so that meteoric water and noise caused by external environment can be eliminated. After such smooth resample, at the spectrum scope of 1 112~1 322 nm, taking band value as horizontal axis and reflectivity as vertical axis, linear equations of rock samples can be obtained. Taking the slopes as the horizontal axis and volume magnetic susceptibility as vertical axis, y=-0.256 3ln(x)+0.913 7 was thus obtained and its equation correlation coefficient is up to 0.78. The result shows that volume magnetic susceptibility is mainly caused by Fe2+, and that the amount of Fe2+ can be almost measured in the spectrum scope of 1 112~1 322 nm that has a good correlation with volume magnetic susceptibility.