Playfield detection is a key step in sports video content analysis, while the playfield presents different colors in broadcast video as a result of illumination variation caused by different cameras and different shooting angles, etc. To address the problem, adaptive GMM is exploited to detect playfield. The proposed algorithm first selects samples in a video clip randomly and extracts the dominant color in the histogram automatically; then the dominant color is modeled by GMM approximately. To adapt the model to the playfield color variation, the model's parameters are updated by incremental EM algorithm in the process of playfield detection. Based on the playfield's detection result, a simple and effective algorithm is proposed to classify the scene in soccer video according to the playfield distribution region in a frame. Experimental results show that the proposed algorithms are effective.