Based on FTIR experiments of diopsides and omphacites at varying temperatures, this paper discussed the incorporation mechanisms of OH defects in clinopyroxene minerals from a new point of view, i.e., thermal expansion. There are three groups of OH absorption bands in clinopyroxene minerals, namely, 3600～3620 cm-1,3500～3540 cm-1, and 3445～3465 cm-1. The OH incorporation mode of Group 1 bands is Si4+ +O2- +1/2H2<->Al3++OH-, while the M2 vacancy is responsible for the OH incorporation mode of Group 3 bands. The OH incorporation mode of Group 2 bands is complex and might be related to several different positions. The OH dipole vibration direction of Group 2 bands is the same as that of Group 3 bands, along the shared edge of M1 and M2 polyhedra,O2—O1. And the OH dipole of Group 1 bands vibrates between O2 and O3 along the edge of M2 polyhedron.