This paper concerns the problem of standing tree volume measurement based on digital image processing. A computer and a camera were used in our work. Before the tree photo was taken, two red color marking labels were attached on the trunk. After the marking points and the tree trunk were extracted, the tree trunk edges were fitted with a high order curve. Then the volume of tree trunk of any height selected with a rectangle can be calculated. The experimental results show that the relative measurement error is low enough. So it is a viable method.