We studied the dielectric and elastic properties of LiKSO4 crystal under various temperature (150-350 K) and pressure (0-10 kbar). An anomalous change of the dielectric and elastic constants was found near the room temperature and 8.2 kbar (correspond to raising pressure) and 4kbar (correspond to releasing pressure). We attribute this anomalous change to the phase transition induced by the pressure. The process of this phase transition is accompanied by large pressure hysteresis.We also obtained the p-T phase diagram of LiKSO4 in these temperature and pressure range. A triple point was found near 3.8 kbar and 281 K.