Abstract: Based on lots of experiences of image interpretation，the relationship between the radar image and the water content，and the imagine rule with different water conditions are found out.In the opinion that all the images can be expressed by color value matrix and the matrix similarity indicates the images' similarity，the method of classifying the water conditions of ground penetrating radar results by matrix similarity is put forwards.The color value matrix is used to extract the image and to calculate the central value of feature vector in different types of water condition.Then，the feasibility on the matrix similarity method to interprete the ground penetrating radar results is verified with good effect achieved in practical application.

Key words: Ground penetrating radar image, Matrix similarity, Image's color matrix, The central value of feature vector