The binary phase diagram of LiNO3-KNO3 are studied by means of differential scanning calorimeter (DSC). The convincing evidence for the identification of new phase has been presented. The phase diagram indicates an intermediate compound KLi(NO3)(2), which melts congruently at 428 K. The coordinates of two eutectic points are 420 K, 47 mol% KNO3 and 410 K, 54 mol% KNO3.