Abstract: In order to measure tree-ring information accurately and quickly, a peak-valley tree-ring recognition method based on gray image is proposed. Firstly, the disc color image is converted into gray image. Then the two-dimensional gray data is converted into one-dimensional gray complement data. Finally, the peak-valley tree-ring recognition algorithm is used to obtain the information of tree age and tree-ring width from the one-dimensional gray complement data. The results show that the accuracy of peak-valley tree-ring recognition algorithm in predicting tree age and tree-ring width is up to 90%. The algorithm is easy to understand and provides a simple and feasible method for obtaining the information of tree-rings from disk image.