Carbon emissions are recognized as a major contributor to global warming. To combat climate change， many countries and regions have implemented regulations to guide enterprises to reduce carbon emissions. Therefore， the compliance or non-compliance with the carbon emission regulations becomes a critical factor in assessing enterprises’ environmental responsibility， especially in a supply chain with a supplier and two competing manufacturers. The downside effect caused by the supplier non-compliance is often attributed to the downstream manufacturers’ fault， thereby motivating the latter to conduct a audit to prevent negative impacts on their goodwill. Based on the competition theory， there are two audit strategies for the two manufacturers： independent audit and joint audit. Specifically， under independent audit， the manufacturers conduct their respective audits and impose penalties independently. Under joint audit， the manufacturers conduct a audit jointly， and impose a collective penalty if the supplier fails their joint audit. Then， which audit strategy should be choosed by the two manufacturers？To answer the above question， simultaneous game model with the supplier and the two manufacturers is used to analyze and compare the equilibrium decisions and the optimal profits under independent audit and joint audit. The study results show that， first of all， there is the feasible region that independent audit is dominant. Moreover， independent audit is a “perfect” audit strategy in this region. That is， independence audit not only can improve the supplier’s carbon reduction compliance but also can benefit the manufacturers and the supplier. Secondly， when joint audit is dominant， it is unexpectedly finds that joint audit is a “imperfect” strategy， i.e.， it is only beneficial to the improvement of the supplier’s carbon emission reduction compliance and the two manufacturer’s profit， even is a “failure” strategy， that is， it is only beneficial to both manufacturers. For this， a carbon emission reduction compliance cost-sharing mechanism based on the purchase price is designed to improve the carbon emission reduction compliance and profit of the supplier， thus allowing joint audit to also become a “perfect” strategy. Finally， whether independent audit or joint audit， the two manufacturers should keep a prudent attitude toward the price premium to prevent falling into the “price trap” and thus avoid the risk of reducing carbon emission reduction compliance.In summary， through this study， it aims to comparative analysis independent audit and joint audit， and then to provide insights for how the two competing manufacturers should conduct a audit to manage the supplier non-compliance with emission reduction.