Abstract: The population density and secretion of lac insect (Kerria chinensis Mahdihassan) in winter and summer generations have been studied in this paper. The research results have shown that the secretion of female adult is about 95% of total secretion, the secretion of larvae is very little, the population density of female adult in late period of winter and summer generations, 20~30 bodies/cm2, is favourable for secretion. In winter generation, the highest secretion of lac insect parasitizing Dalbergia balansae Prain is about 10.60mg/♀, and its population density is 25 bodies/cm2; in summer generation, the highest secretion is 15.64mg/♀, and its population density is 27 bodies/cm2. Lac insect smoothly secrete in winter generation and flourishingly secrete in summer generation. In summer generation, there is a high secreting period in pregnant female 3~4 stages, population density is 35~40 bodies/cm2. Other biological characters of lac insect have also been discussed in this paper.