Many internal defects maybe arise in railway track working, which usually have different shapes and distribution rules. To solve the problem, an intelligent detection method is proposed for internal defects of railway track based on generalization features cluster in this paper. Firstly, defects are classified and counted according to their shapes and locations features. Then, generalized features of defects are extracted and formulated based on the maximum difference between different types of defects and the maximum tolerance among same types of defects. Finally, extracted generalized features are expressed by function constraints, and formulated as generalization feature clusters to classify and identify internal defects of the railway track. Furthermore, a reduced dimension method of the generalization features clusters is presented too in this paper. Based on the reduced dimension feature and strong constrained generalized features, the K-means clustering algorithm is developed for defects clustering, and good clustering results are achieved. To defects in the rail head region, its clustering accuracy is over 95%, and the Davies-Bouldin Index (DBI) index is small, which indicates the validation of the proposed generalization features with strong constraints. Experimental results show that accuracy of the proposed method based on generalization features clusters is up to 97.55%, and the average detection time is 0.12s/frame, which indicates it has good performance in adaptability, high accuracy and detection speed under the complex working environments.