Abstract: There are 186,000 hectares of plane broadcasting forest that are all pure Yunnan Pines in Liangshan. They are seriously harmed by Tomicus piniperda L. in recent years. This paper presented a systematic investigation into the occurrence and the harming effects of Tomicus piniperda L. We found that the occurring area of this insect in Liangshan reached 51,000 hectares, among which 5,100 hectares were heavily harmed, 18,800 hectares were harmed on a medium level and 27,100 hectares were slightly harmed. The infection of this insect can be found throughout the whole plane broadcasting area in Liangshan and is rapidly spreading. In light of this situation and the reality of Liangshan Prefecture, and based on the past experience in the prevention of this insect, we correspondingly offered some comprehensive preventive measures.