On one hand, goalmouth detection is a kind of high-level semantic concept detection methods in sports video, on the other hand, data mining for video processing that can benefit video analysis is a promising research frontier. In this paper, a robust method is proposed to detect the presence of goalmouth in field-ball game video based on fuzzy decision trees. Balance process is added in training procedure. The experiment result shows that our algorithm can improve the classification when comparing with the threshold based algorithm and the decision tree based algorithm. Fuzzy rules can also be easily deduced from the constructed tree to interpret the classification model.