The effects of high pressure up to 24 GPa on carbon nitride were studied usingin situmicro photoluminescence (PL) and infrared (IR) absorption measurements at room temperature. The experiments indicate pressure-induced PL quenching with pressure increasing from 0 to 7 GPa, but the PL remains unchanged from 7 to 24 GPa. The PL results display the pressure effect of PL enhancement after release of pressure to ambient atmosphere. The IR absorption bands broaden toward low frequency after release of pressure. These may be explained by using the PL model of undistorted sp2clusters, which, as PL centers, undergo distortion under pressure and pressure-induced local atomic rearrangement in the sample. ©1997 American Institute of Physics.