This paper presents an efficient method of obstacle recognition system and HRI (human robot interaction) system specialized for biped walking robot. This method transmits the information regarding obstacle conditions to a biped walking robot. In the present paper, we describe a cascade of boosted classifier using adaboost algorithm as a obstacle region extracting module from input images. Besides, PCA is applied as a feature extracting module from the obstacle region and a hierarchical support vector machine is applied as an obstacle recognizing module. The data from vision system is combined with information from other sensors and the walking assist commands transmit to the biped walking robot. From the results of experiments, the proposed method can be applied to biped walking robot effectively.