Sexual dimorphism of body size and body shape widely exists in the animal kingdom. Generally speaking, females should exhibit a greater abdominal volume than males to hold the progeny, when compared with females, males should exhibit more developed attributes that enhance mobility and mating success. We studied sexual dimorphism of body size and body shape in Sacalia quadriocellata based on 43 (22♀♀21♂♂) adults collected from Qiongzhong county in Hainan province. We measured 19 morphological variables on these specimens. As expected, our data indicate that the shell provides a larger abdominal volume relative to shell size in females than in males. In males, larger shell openings offer more freedom to the limbs and to the tail, longer hind limbs enhance mobility, bigger head might serve to clam the female, and the more posterior cloaca in the tail most likely facilitate copulation. All of these characteristics presumably enhance mating success. Our main conclusion is that sexual dimorphism of body size and body shape existed in Sacalia quadriocellata.