Abstract: Soil carbon sequestration is the key to improve soil fertility and to secure and achieve sustainable and stable crop productivity. Identifying the synergistic effects of soil carbon sequestration on crop yield improvement in agricultural soils could provide scientific basis for soil fertility improvement sustaining and improving crop productivity in different regions. In agricultural soils, soil carbon sequestration is mainly affected by climate, soil properties, management practices (especially fertilization and tillage) and cropping and rotation. Soil carbon sequestration is significantly correlated with crop productivity, showing obvious impact on crop productivity synergistically. There is an obvious threshold value of the synergistic effect of soil carbon sequestration on crop yield improvement. In addition, the threshold value of soil organic carbon varied among regions. For instance, the threshold value of soil organic carbon is approximately (ca.) C 44–46 t/hm² for the Northeast of China, ca. C 26–28 t/hm² for the Northwest of China, ca. C 22 t/hm² for the North China and ca. C 35 t/hm² for the South of China. Based on the results from empirical equations and model simulations, the magnitude of crop yields improvement by each 1.0 C t/(hm²·a) of enhanced soil carbon sequestration is averaged 0.7 t/hm² for wheat, maize and rice yields. It indicated that the synergistic effects of soil carbon sequestration on crop productivity improvement was regulated by these relevant environmental factors and management practices. Understanding the underlying mechanisms of soil carbon sequestration process and interaction of the synergistic effects on crop productivity is important for guiding the improvement and enhancement of soil fertility, crop productivity and nutrient resource use efficiency. Future studies should be focused on identifying the attainable potential of soil carbon sequestration, further revealing the mechanisms of soil carbon sequestration under intensive cropping conditions, paying more attentions to the effects of soil carbon sequestration in deep soil on the improvement potential and contribution of crop yield, and quantifying the contributions and controlling theory of environment or anthropic practices to the interactions between soil carbon sequestration and crop yield improvement.