A structural phase transition in crystal LiKSO4 at Tc = 195 K was confirmed by NMR experiment previously. In this article, the temperature dependence of the electric field gradient tensor at lithium site in the range of 110-300 K is reported, and combined with a simplified ion crystal model the crystal structure is discussed. It is shown that even in the room temperature phase, the lithium position should be at (2/3, 1/3, 0.706) instead of the position at (2/3, 1/3, 0.849) suggested previously by Bradley. The phase transition is attributed to the displacement of lithium ions. The space group of the low temperature phase may be R3.