By using totally locating method and single tree competition index model, this paper studied the competition intensity of Mongolian pine forests in Hulun Buir sand region of Inner Mongolia, with the fire-disturbed Mongolian pine forest as a case.

Based on the growth theory of Von Bertalanffy, this paper built the single tree growth model for Cryptomeria fortunei stands by using simple competition index, By means of general rule that density affects stem shape, analysed the relationship between simple competition index and shape index,and established shape index model, so as to provide a new way for volume measurement of standing trees.