The luminescent functional crystal was produced by the organic guest molecules conformation control in the inorganic host crystal matrix. Inorganic host-organic guest crystals were successfully prepared and luminescence spectra were investigated. These crystals had a phosphorescent property in room temperature by 254 nm UV irradiation. In this system, the potassium sulfate host matrix was effectively inhibited the molecular vibration of organic guest molecules by interaction between K+ and π-electrons. In addition, control of the luminescence wavelength (both fluorescence and phosphorescence) was achieved by controlling the structure of organic molecules which were taken in anorganic compound-containing inorganic crystal. Specifically, theorganic compound-containing inorganic crystals with 2-aminobenzenesulfonic acid and 2-naptylamine-1-sulfonic acid as a guest had a phosphorescence band of 455 nm and 510 nm, respectively.