The fluorescence emission and X-ray diffraction of magnesium 8-hydroxyquinoline complex (Mgq(2)) have been measured at high pressure up to 14 GPa. It has been found that pressure can influence the emission dramatically. At relative lower pressure (less than 2.5 GPa) the fluorescence of Mgq(2) changes slightly, but the emission drops quickly with increase of the pressure when the pressure gets higher than 2.5 GPa. The results of in situ energy dispersive X-ray diffraction at high pressure with synchrotron radiation indicate that there is a phase transition at about 2.5-3 GPa for Mgq(2) crystal.