[[abstract]]Ko fight is not only an important and interest part in Go, but also one of the key issues in order to improve the level of Go program. There is a great relationship between Ko and Ko threat. In other words, the complexity and fun of Ko are usually based on finding Ko threat. Damage Ko is one kind of Ko threat that occurs and is used frequently. Because of the property of damage Ko, it’s getting more complex when we deal with the benefits of the Ko threats. Following the research of S. C. Huang in National Taiwan Normal University for Ko fight, we furthermore consider the usage of damage Ko and find out the strategies for Ko fight by showing the flow diagram of Ko fight and the principle of minimax search. Our prototype program can calculate the optimal benefit quite fast in some cases, and choose a correct Ko threat to against opponent when Ko fight happened. We can find the best solution when damage values of the Ko threats are the same. On the other hand, the number of Ko threat that we can process in 7 minutes by our search method is about 16 for each player when the damage values are different. The experimental results show that we can approximate the best solution by our heuristic method with an average error less than 0.1.