Objective: To investigate the clinical status and risk factors of delayed lactation initiation (DOL) in pregnant women with gestational diabetes mellitus (GDM), and to construct a simple risk prediction model, so as to provide reference for clinical nursing of DOL in gestational diabetes mellitus. Methods: A total of 388 pregnant women with gestational diabetes mellitus who were filed in our hospital from January 2015 to December 2018 were selected by convenient sampling method. The data of general demography, delivery and lactation start-up time of pregnant women were collected and analyzed by SPSS 22.0 software. Results: The incidence of DOL was 25.2% in 388 pregnant women with gestational diabetes mellitus. Through univariate analysis and logistic regression analysis, we can construct a risk prediction model including five risk factors: old age (≥35 years old), overweight (BMI ≥30 kg/m2), premature delivery (28–37 weeks), anxiety and depression. The risk scores of each factor are 3, 3, 4, 3 and 3 in turn, with a total score of 0–16. According to the model score of 95% CI with or without DOL, the risk model can be divided into three grades: low risk (<5 points), medium risk (5–8 points) and high risk (>8 points). The corresponding incidence rates of DOL are 8.1%, 22.1% and 53.4% respectively. The ROC analysis results of model score and DOL show that the area under the curve is 0.757, 95% CI is 0.703–0.811, and the Yoden index is the largest when the score is (>6.5 points), which is 0.426. Conclusion: The incidence of DOL in pregnant women with gestational diabetes mellitus is relatively high. The new risk prediction model has the ability of distinguishing and predicting. Clinical nurses can carry out preventive nursing according to this model as early as possible.