Objective To explore the effect of nursing intervention based on the transtheoretical model of change on pregnant women at high risk of gestational diabetes mellitus(GDM). Methods A total of 88 pregnant women at high risk of GDM were selected and evenly divided into two groups according to the periods of obstetric examination. The control group received routine nursing intervention, while the intervention group received nursing intervention based on the transtheoretical model of change. The incidence rate of GDM, 2-hour plasma glucose (2h PG) after 75 g oral glucose tolerance test (OGTT), GDM self-management ability scores and self-efficacy scores were compared between the two groups after intervention. Results After intervention, the incidence rate of GDM had no significant difference between the 2 groups (P>0.05), while 2h PG values were significantly lower (P<0.05), GDM self-management ability scores and self-efficacy scores were significantly higher in the intervention group than in the control group (P<0.01 for both). Conclusion Nursing intervention based on the transtheoretical model of change can help improve self-management ability of pregnant women at high risk of GDM, increase the level of self-efficacy, and help them effectively control their blood glucose level to a certain extent.