Based on the dynamic evolution of the grey hazy set, a line feature extraction algorithm is proposed for the knowledge expression of uncertain information by simulating the gradually cognitive process of human. The algorithm eliminates the uncertainty of the information in unknown environment with the geometric constraint gradually by producing expression of different cognitive stage through dynamic evolution of the grey hazy set. As the manifestation of environmental information, the line-segment feature is detected by self-organizing mapping with main direction exacting based on the grey correlation degree. The example in the corridor environment is provided to verify the effectiveness of the proposed algorithm in simulating human’s intelligence of environmental information expression and reasoning.