Abstract: The author of this paper has given an assumption that the log dropout process may be divided into two stagges.In april,1981,the experiment was conducted in the laboratory of the North-Eastern College of Forestry and proved that there exist two stages. On the basis of the experiment,the author further presents the theory of three stages in the log dropout process as follows: 1. The first stage:the toggles are tilted and turned around one track of the conveyor(Fig.1,b).The tilt of the toggles gives the log a selfdropout power. 2. The second stage:the toggles are rotated around the pull organ (chains or wire rope,Fig.l,c).It gives the proper condition to drop the log. 3. The third stage:the log rolled down from the toggles. This paper points out that the first and the second stages are most important for log dropout. Finally some parameters for determing the log dropout performance,such as log dropout time consumption,log diameter,log eccentricity and the log curvature are discussed in the paper.The experiment and analysis show this type of the log dorpout system by gravity with collapse of the toggles gives a minimum dropout time consumption and all kinds of logs can be discharged from the conveyor.