Ko plays a very important role in Go, but most computer Go programs still cannot handle ko fight so far. Utilizing the principle of the minimax search, we obtain some best strategies for the simple one-point ko situation, enabling computer Go programs to gain maximum or loss minimum profit when dealing with the simple one-point ko situation. In order to achieve our goal, we define the value of a move, the value of a ko and the value of a ko threat precisely as the foundation of our discussion. We also dicuss in detail the strategies for using ko threats during the process of the ko fight.