Objective To explore the impact of continuous intervention under the guidance of the integrated theory of health behavior change (ITHBC) on patients with gestational diabetes mellitus (GDM). Methods This was a prospective randomized controlled trial involving 120 patients with GDM who were admitted to Zhengzhou Central Hospital Affiliated to Zhengzhou University from January 2023 to March 2025 were included in the study. They were randomly divided into the conventional group and the study group according to the random number table method, with 60 cases in each group. The control group was given conventional intervention, while the study group was given continuous intervention under the guidance of the ITHBC theory on the basis of conventional intervention. The changes of health behaviors, self-care ability and emotional state before and after the intervention in the two groups were compared, and the occurrence of adverse maternal and infant outcomes after delivery in the two groups of GDM patients was statistically analyzed. Result After intervention, the scores of the six dimensions of the health promotion lifestyle scale-Ⅱ (HPLP-Ⅱ), the scores of each dimension of disease in the self-care ability scale (ESCA), and the total score of ESCA in the two groups were all increased compared with those before intervention (all P＜0.05), the Hamilton anxiety scale (HAMA) scores and the Hamilton depression scale (HAMD) scores were all decreased compared with those before intervention (all P＜0.05). After intervention, the above-mentioned indicators in the study group were all significantly lower than those in the conventional group (all P＜0.05). The total incidence of adverse maternal and infant outcomes in the conventional group [25.00%(15/60)] was significantly higher than that in the study group [10.00% (6/60)] (P＜0.05). Conclusion The continuous intervention under the guidance of the ITHBC theory can significantly improve the health behaviors, self-care abilities and emotional state changes of patients with GDM, and reduce the risk of adverse maternal and infant outcomes.