In a soccer robot game, the environment is highly competitive and dynamic. In order to work in the dynamically changing environment, the decision-making system of a soccer robot system should have the features of flexibility and on-line adaptation. This paper proposed a strategy-based decision-making system for a soccer robot system. The decision system is based on the proposed self-organizing fuzzy decision tree (SOFDT). Due to event-driven strategies, the proposed decision-making system has the advantage of flexibility. The proposed SOFDT possesses simple, apparent, and fast generation/reasoning processes. The resultant system is a self-organizing strategy-based decision-making system. According to decision results, SOFDT can on-line modify its parameters and structure for achieving better adaptability and improvement. The performance of the proposed systems was verified by applying them to the simulation and experiment of 3-to-3 robot soccer games. The results are satisfactory.