In order to investigate the radial farthest detection distance and the appropriate detector arrangement for diffuse reflectance spectroscopy in detecting effective information from internal tissues, a human subcutaneous tissue model was con- structed, and the transmission process of 760 nm near-infrared light in the tissues was simulated by using the Monte Carlo (MC) method. Two combined fat-muscle MC models were established according to the optical properties of different tissues. In this model, placing the detector approximately 3 cm, or closer, from the light source allows for the acquisition of valid information about the interior of the tissue. The distribution, number and residual weights of escaping photons at different distances were analyzed in different cases. The results showed that under this model, placing the detector at a distance of about 3 cm, or closer, from the light source can effectively acquire photons inside the tissue. Finally, based on the results of the MC simulation, three detector arrangements that can be applied to noninvasive blood flow or blood oxygenation detection were analyzed and de- signed. Through comparison, it is found that the hybrid multi-light source-multi-detector arrangement design can not only collect the diffuse light from the tissue more effectively and provide a more uniform photon distribution, but also the design can maxi-mize the number of detectors and realize the detection of a larger area of the same depth of the tissue, compared with the single light source-multi-detector, which provides ideas for the design of spectroscopic instruments for noninvasive detection of near- infrared blood flow or blood oxygenation.