This paper deals with the biological investigations and life history of pine caterpillar,in Hunan province during the investigating period 1954—1957. Pine caterpillar is very common in Hunan province.They are usually two or three generations a year,and the larval stage varies from 6 to 9 instars,most are six ones.The periods and biological characters of each stage and generation are studied. In spring,most of the cocoons are formed above the ground in southern part of Hunan,and on crown in northern part of this province. During the hiberating period and in fine weather,the larvae may climb out and feed on the pine leaves.If the temperature keeps at 28℃,the egg stage is about 8 days and the larvae stage 31.9 days;at 25℃,the egg stage is about 9—11 days;at 30℃,about 6 days for egg stage and 26.233 days for larvae stage.When the relative humidity is 84%,the hatching percentage will reach its height;when it is 100%,the death rate will come to its height.Pine caterpillar grows quickly in the light place and slowly in the dark. There are many species of natural enemies of which egg parasites has more than 8 species and larvae parasites about 6 species. In the.end of this paper,a preliminary study of prognostic is given.