Abstract: This paper describes the freezing injury of Pinus yunnanensis influenced by unusual temperature (about -5.2℃). There were five main respects; 1. the morphological characteristics of P. yunnanensis after suffering from freezing; 2. how to judge the frostbite degree of an individual by the external morphological characteristics; 3. the relations between the frostbite degree and the height above sea level; 4. the destroyed conditions of the meristematic cells and the material variation in living cells among distinct injured individuals which are planted on the same elevation; 5. exploring the renewal posibility of the injured plants by their inner characteristics. According to the internal and external factors which cause the injury of P. yunnanensis, the writer provides some theoretioal bases for further productive measures.