In this paper, we determined the age of an overweight female narrow-ridged finless porpoise Neophocaena asiaeorientalis sunameri remains which was found in February 2016 in Shanghai Chongming Island, then compared its somatotype parameters, thickness of the abdomen fat and liver tissue with normal individuals of the same age. The analysis shows that the N. asiaeorientalis sunameri is two years old, its body length is 115.0 cm, body weight is 29.9 kg, the largest body girth is 86.2 cm, body mass index (BMI) is 22.6 kg/m², body girth index (BGI) is 75.0%, thickness of the abdomen fat is 3.5-4.3 cm, all of these parameters are significantly higher than other eight remains in the same estuary. Based on the methodologies and criteria of judging obesity in humans, such as the BMI, a common measure of obesity, we found that this N. asiaeorientalis sunameri is obese. The liver weight of the experimental sample is about 3.3% of the body weight, fat fraction in liver reaches up to 9.27%±1.67%, fat accounts for the liver section also reaches 40.81%±2.09%. Separately, each percentage is significantly higher than normal or control individuals, the multiples are 1.4 times, 2.63 times and 1.75 times in sequence. In our ocular inspection, the liver surface of experimental sample is rough, it reveals intenal lesions with short myofiber and hepatic steatosis. Paraffin sections show that the mass eosinophil infiltration in the tissue in low-power scan; At high magnification, the hepatocyte in mild lesion area occurs to obvious pathological cavitation, only completely necrotic hepatocyte can be seen in highly pathological change area. Research indicated that this obesity N. asiaeorientalis sunameri has evolved serious adiposis hepatica which was correlated to its somatotype parameters and thickness of the abdomen fat. These findings have a certain guiding significance for finless porpoise's domestication and ex situ conservation.