Pregnant women are at elevated risk of severe influenza-related complications and maternal influenza vaccination protects mothers and infants. Nevertheless, the global maternal influenza vaccination rates remain critically low. This cross-sectional survey, conducted in Shanghai during 2023-2024, applied the Health Belief Model (HBM) to evaluate the attitudes and determinants of seasonal influenza vaccination among 3219 pregnant women. Only 10.9% (351/3219) accepted the vaccination, while 89.1% (1851/3219) declined, including 35.4% (1017/3219) who expressed uncertainty. Key facilitators of acceptance included higher education (graduate degree and above: adjusted odds ratio (aOR) = 2.49) and a greater total influenza knowledge score (aOR = 1.07). Strong HBM constructs, including perceived susceptibility (aOR = 1.53), perceived severity (aOR = 1.66), and belief in vaccine benefit (aOR = 2.55) significantly predicted vaccine uptake. The most influential factor was cues to action (aOR = 8.55). Conversely, safety concerns for maternal and fetal health dominated hesitancy, overshadowing other barriers. As the first HBM-based study to assess the attitude to influenza vaccination among pregnant women in China, these findings revealed low baseline awareness and confidence among Shanghai's population of pregnant women. This study highlighted an urgent need to strengthen provider-patient communication to amplify "cues to action," and integrated vaccination advocacy into routine prenatal care. Addressing these barriers could align vaccination rates with global maternal health priorities, leveraging dual protection for mothers and infants.