Abstract: Among the methods involved in estimating the height of each age gradation by stem analysis,the height in a certain year between two disks is considered as the height of the upper disk by using the traditional method of"height curve line",which produces a plus systematic error.Although a"Modification Method" by Mr.Cheng Zichun makes the error become plus and minus ones,the absolute error is not contracted.Without considering the change of tree growth and replacing the actual stem height by a certain height,in fact,it is the same as the former,its result from calculation can not be used to analyze the tree growing process exactly.A lot of materials in pratice shows that the height can be estimated by using the method of vertical section chart,which possesses a scientific grand,moreover,it is convenient,accurate and direct in use,especially suitable for some fast-growing species such as Chinese fir,Masson's pine ect.