Fringe projection profilometry (FPP) has been widely used for three dimensional (3D) imaging and measurement. The
fringe acquisition of FPP mainly depends on the diffuse light from the surface of objects, thus the characteristics of
object surface have significant influence on phase calculation. One of the essential factors related to phase precision is
modulation index, which has a direct relationship with the surface reflectivity. This paper presents a comparative study
which focuses on the modulation index of different materials. The distribution of modulation index for different samples
is statistical analyzed, which leads to the conclusion that the modulation index is determined by the diffuse reflectivity
rather than the type of materials. This work is helpful to the development of effective de-noising algorithms to improve
the measurement accuracy.