It is of great significance to study the carbon emission reduction effect of renewable resources utilization in promoting the formation of differentiated emission reduction paths suitable for China’s national conditions and achieving the double-carbon target. Against this background, in-depth exploration and assessment of the carbon emission reduction effect and mechanism of renewable resources utilization is an important issue that urgently needs to clarify. This study regards the alternative utilization of renewable resources to primary resources as an environmental pollution-control activity, and constructs the social utility function to derive the influence mechanism of renewable resources utilization on carbon emission reduction based on the optimal control theory model. The theoretical derivation results indicate that carbon reduction effect of renewable resources utilization depends on the coefficient of resources consumption in the process of renewable resources utilization. When the carbon emissions reduced by renewable resources substitution exceed the carbon emissions caused by the new consumed resources during the recycling process of renewable resources, that is, when the benefit of carbon reduction from the renewable resources substitution is greater than the cost, the carbon reduction effect exists. Secondly, using Chinese provincial panel data from 2005 to 2019, this paper empirically examines the comprehensive impact of renewable resources utilization on carbon emissions, and further analyzes the effect mechanism, threshold effects, and heterogeneity. The empirical test results indicate that: 1) Overall, there is a negative correlation between the level of renewable resources utilization and carbon dioxide emissions in China. Renewable resources utilization can effectively inhibit carbon emissions intensity, and the benefit of carbon reduction from renewable resources utilization exceeds the cost. 2) From the perspective of mechanism, green technology innovation and industrial structure upgrading have important intermediate effects on renewable resources utilization affecting carbon emissions. Renewable resources substitution can suppress regional carbon emissions intensity by promoting green technology innovation and improving the level of industrial structure. 3) The threshold effect test finds that there is a certain threshold effect of renewable resources utilization on carbon emissions when selecting the level of renewable resources utilization and economic development level as threshold variables. The carbon reduction effect of renewable resources utilization becomes more evident when surpassing a specific threshold value, indicating that the relationship between renewable resources substitution and carbon reduction is not linear. 4) Heterogeneity analysis further reveals that the differences in geographical location and the level of circular economic development make the carbon emission reduction effect of renewable resources utilization exhibit heterogeneity characteristics. The carbon emission reduction effect of renewable resources utilization is more pronounced in the eastern region (compared with the western region), the southern region (compared with the northern region), and regions with higher levels of circular economic development. Based on the above research results, this study puts forward policy suggestions, including improving the level of renewable resources utilization and the quality of economic development, strengthening support for technological innovation, promoting the upgrading of the industrial chain, and formulating differentiated strategies for renewable resources utilization.