Abstract:Continuously moving skidders,mainly J-50 tracked skidder and J-80wheeled,are widely used in extracting operations in the forests of northeastern China and result in soil erosion and humus loss which seriously affect stand regeneration and growth of remaining crops.Using Grey Theory an investigation was undertaken to analyze soil compaction and seedling growth in the stands under such a harvesting system.It was found that extracting operation caused less damage to soil structure and less effects on the height growth of seedlings by the use of tracked skidders than wheeled ones.