The high carbon emissions of the construction industry affect China’s sustainable development. Therefore, reducing the carbon emissions of the construction industry is crucial for China to achieve “carbon peak” by 2030 and “carbon neutrality” by 2060. To understand the factors that affect contractors’ willingness to reduce carbon emissions. This study is based on the Theory of Planned Behavior (TPB) and incorporates three potential influencing factors: personal norms (PN), government regulation (GR), and policy support (PS). It constructs a structural equation model (SEM) to predict the influencing factors of carbon emission reduction intentions (CERI) among construction contractors. This study analyzes the key factors and mechanisms influencing construction contractors’ CERI. The study collected 311 valid questionnaires, which are suitable for SEM research, and the results indicate that: The results show that the model proposed in the study has an explanatory rate of 69% for developers’ willingness to reduce carbon emissions. The most significant influencing factor on construction contractors’ CERI is GR, followed by PS, subjective norms (SN), and perceived behavioral control (PBC). PN and behavioral attitude (BA) towards behavior do not significantly impact CERI. SN mediate the relationship between GR and CERI, while PBC mediates the relationship between PS and CERI. The research findings can guide the government and construction contractors to improve carbon emission reduction governance mechanisms and achieve peak carbon emissions and carbon neutrality.