The optical parameters of biological tissue are closely related to tissue’s physiological, biochemical and pathological process. We could learn about the internal structure and characteristic of the biological tissue by determining and reconstructing the 3D image of optical scattering and absorption coefficients. Based on the frequency-domain near-infrared spectroscopy, the imagent system of ISS Corporation in USA and the technology of multi-source and multi-detector were used to complete the experiment. In the experiment, a tank was filled with milk and a little ball was put into the milk, we shined the modulated laser signal which wavelength was 830 nm into the milk and detected the intensity and phase of the emergent light. Then, optical diffusion tomography was used to reconstruct the location of little ball in the milk by calculating the optical scattering and absorption. Experiment results showed that we could calculate the optical scattering and absorption coefficients of the milk and the little ball accurately by using the frequency-domain near-infrared spectroscopy. And we could also locate the position of the little ball in the milk. Therefore, it was considered that the frequency-domain near-infrared spectroscopy could be applied in the field of agricultural product quality detection such as analysis the lesion location of the fruits and vegetables.