Playing multiple games simultaneously is popular, but we hardly know how people act in this situation to reach mutual cooperation in the long run. To answer the question, we conduct a series of experiments on multi-game contact. The results indicate that the number of information sets in the stage game and the payoff structure are important. We find that for making mutual cooperation subjects employ two types of TFT strategies, which simplify the complicated contact. In these strategies, they avoid separating behavior such as cooparating in one game but deviating in the other. This makes it easy for the opponents to understand thier cooperative intention
