The sensitivity expression of spatial-resolved diffuse reflectance to first-order scattering parameter was derived and numerically analyzed based on the P3 approximation of transport theory,and the influence of scattering parameter on the P3 approximation and diffusion approximation reflectance were also compared.The results show that:the sensitivity is distinct with that of the diffusion approximation in the region of about two transport mean free paths;the sensitivity to scattering parameter equals zero at the distance about four transport mean free paths which differs with the diffusion approximation;the optimum source-detector distance decreases with the increase of the scattering coefficient,and this change becomes more obvious with lower absorption.The research has theoretical significance to obtain absorption information of tissue with diffuse reflectance at the optimum source-detector distance.