The technique of histogram equalization (HE) is widely used in the field of image enhancement

the method is introduced into the gradient field in this paper

so image details are distributed in each gray level uniformly.Moreover

the characteristics of the histogram of gradient magnitude are studied

according to the right-skewed distribution of gradient magnitude

the gradient field is equalized by two intervals.In terms of the threshold's selection

numerical characteristics of frequency distribution are considered

two standards of the interval threshold are proposed

which can divide the gradient magnitude into the interval with low magnitude and the interval with high magnitude.On the process of the reconstruction of target gradient field

matrix transform method is proposed

which substitutes the traditional method difference and iteration method

the proposed method can decrease the algorithm's time complexity.The experimental results show that the method this paper proposed can make image details enhance effectively.