In this paper, we have proposed a simple method to determine what charges the carriers in ionic conductor possess by analysing the relation of voltages between middle point of the sample and its two terminal surface electrodes. By using this method and considering that α-LiIO3 single crystal can be regarded as a quasi 1-dimension conductor, it has been found that there are two kinds of carriers in α-LiIO3 single crystal. One of them is the interstitial Li ion which hops among the intersites in a zigzag channel along c-axis. The other is the Li vacancy which exchanges positions with Li ions at lattice sites also along c-axis. We have measured the electrica conduction properties from -100℃ up to room temperature. The results are analogous to those obtained above room temperature.