The possible high pressure modifications of Lithium Iodate (LiIO3) were surveyed in the high pressure and high temperature ranges up to 40 kbar and 750℃. Two high pressure modifications have been observed. The first is found in the range of 1.5-4.9 kbars and 310-450℃, while another appears in the pressure range above 15 kbars. The phase boundries were determined by DTA and quenching method. The diagram published abroad in 1969 have been corrected and the stability of each phase at high pressures and high temperatures has been discussed.