The brown soft scale, Coccus hesperidum L. (Homoptera: Coccidae) is an economically important insect pest of Arabica coffee in Son La province. The biological characteristics of brown soft scale was inves,tigated under laboratory conditions at Agricultural Department of Tay Bac University during 2009 - 2010. The life cycle of brown soft scale, Coccus hesperidum on coffee seedlings was 69.04 days at 25°C, 85 percent RH and 50.72 days at 30°C, 85 percent RH. Females can reproduce without mating. The brown soft scale has high fecundity. When reared on coffee, each female of brown soft scale Coccus hesperidum can lay 72-325 eggs and with high hatching rate (71.0 percent - 93.5 percent). Eggs hatched in 3 - 7 days after laid and the highest hatching rate was on the fourth day (43.39 percent). The estimated threshold temperature for development was 11.16°C. The total effective temperature for