Generally, the influence factors of the reflectance spectrum of rocks and minerals can be divided into the decisive factors related to composition and content, and the variant factors, including the particle size, roughness, observation angle and surface morphology. The study is focused on the relationship between the reflectance spectrum and the particle size of Anshan iron ore. Firstly, the reflectance spectra of the two main iron ores (hematite ore and magnetite ore) with different particle sizes are obtained by SVC HR-1024. Then, the influence of particle size on the reflectance spectra of both hematite and magnetite is analyzed. The sensitive waveband and stable waveband of the reflectance spectra related to particle size are extracted. The study indicates the following results. Firstly, the effects of particle size on the reflectance spectra of hematite and magnetite are different. For the hematite, the reflectance decreases with the particle size increase when the particle size is in the range of 0.03 to 1 mm. The effects are different in different waveband for the reflectance spectra of hematite. In the wave range of 350~550 nm, the particle size’s effect can be, neglected and this waveband can be regarded as the stable waveband. The influence is weak in the range of 550~950 nm and become obvious in the 950~1 250 nm range. In the range of 1 250~2 500 nm, the reflectance changes obviously with the particle size. Therefore, this waveband can be regarded as a sensitive waveband. However, when the particle size of the hematite is larger than 1 mm, the particle size’s effect decreased obviously without correlation. For the magnetite, the reflectance changes weakly with an amplitude of less than 3% when the particle size is in the range of 0.03 to 4 mm. There is no correlation between the reflectance and the particle size. This study revealed the quantitative relationship between the reflectance spectrum and the particle size for Anshan iron ore. The results can provide the foundation for improving the inversion accuracy of the ore grading for the Anshan iron.