Abstract: Objective To investigate the effects of diet and exercise intervention on body weight and perinatal outcome in patients with gestational diabetes mellitus (GDM) under TTM model. Methods A total of 124 pregnant women with GDM who were admitted to our hospital from December 2015 to December 2017 were enrolled and divided into the conventional group (n=63) and the intervention group (n=61) according to the random number table method. Among them, the conventional group were given regular intervention guidance, while the intervention group were given diet and exercise intervention under the TTM model. The knowledge of the disease-related knowledge during the investigation, the general situation before childbirth, the laboratory test indicators after the intervention, the perinatal outcome, and the general condition of the newborn of the two groups were observed and compared. Results The increase of BMI and BMI before childbirth in the intervention group were significantly lower than that in the conventional group [(25.37±0.93) kg/m² vs. (26.14±1.04) kg/m², (4.12±1.24) kg/m² vs. (5.37±1.03) kg/m²; t=4.341, 6.144, all P<0.001]. The number of insulin users and the re-admission with poor control of sugar were significantly less than those in the conventional group (6 vs. 15, 9 vs. 23; χ²=4.301, 7.659, P=0.038, 0.005). The number of pregnant women with hypertension and polyhydramnios in the intervention group was significantly lower than that in the conventional group (4 vs. 12, 2 vs. 13, P=0.031, 0.007). Conclusion Diet and exercise interventions under the TTM model can effectively reduce the increase in BMI during pregnancy, improve blood sugar levels and reduce adverse outcomes, thus promoting maternal and infant health.