Laboratory studies were carried out in Nghe An on the biological behaviour of the predatory stink bug Andrallus spinidens (Fabr.). The first instar nymphs did not feed, the second, third, fourth, fifth instar nymphs and adult sucked at the abdomen (1, 5 and 6) or chest (3) of the Lepidopterous larvae. Before mating, males antennate females until females agree. Mating lasted 360 minutes, the fastest 30 minutes, average 101.71 minutes. Females laid egg masses on the net cover of the breeding box or on the breeding box. Lack of food during 1 - 3 days, resulted in the death of all of second and third instar nymphs. Fourth and fifth instar nymphs attacked each other, the stronger individual attacked the weaker one, the rate of females attacked males was 20 percent higher than males attacked females.