Soil fertility is one of the most important factors determining crop production. Maintaining and improving soil fertility, which has become an increasing focus for agricultural scientists, is crucial for food security and sustainable agricultural development in China. Soil organic carbon (SOC) and nitrogen (N) directly affect soil fertility and ultimately crop yield, and thus are considered as important soil quality indicators. With the concerns on global warming and environmental pollution, more attention is being paid on enhancing SOC sequestration and improving N use efficiency (NUE) in cropland. Currently, conservation tillage is widely regarded as an important part of sustainable agriculture and has been adopted by many countries, due to its benefits in conserving soil, saving water, fuel and energy, and protecting the environment. Numerous studies have indicated that conservation tillage (i.e., no-till and minimum tillage) increases SOC and total N storages by reducing soil disturbance and increasing residue retention. Thus, a deep understanding of the mechanisms of conservation tillage on enhancing SOC sequestration and NUE is of fundamental significance for soil fertility assessment. However, there are still controversies about the effects of conservation tillage on SOC sequestration and NUE, mainly due to the diverse climates, soil types, cropping systems, and experimental durations. This paper provides a review about the research progresses of conservation tillage effects on SOC content and decomposition (e.g., CO₂ and CH₄ emission), total N content and mineralization (e.g., NH₃ volatilization, N₂O emission, and NO₃^- leaching), and the relationships between SOC and N processes (e.g., C/N stratification) in farmland systems. Meanwhile, this article also assessed factors and mechanisms that influence SOC and N use. Although studies on conservation tillage have been conducted more than 30 years, there are some gaps between China and the other countries, especially on SOC and N processes under conservation tillage systems. Because of the large differences in experiment conditions, the mechanisms of tillage effects on SOC sequestration and N use are not well understood. Furthermore, systematic studies on carbon and N transformations in the soil-plant-atmosphere-continuum are rare under different tillage systems, which make it difficult to conduct in-depth studies of conservation tillage. Meanwhile, considering the emissions of agricultural practices, few papers have assessed the ecological effects of conservation tillage on the interactions between C and N processes. Therefore, it is necessary to study the underpinning mechanisms that govern tillage effects on SOC sequestration and N use. Our analysis showed that the potential researchable areas and priorities on the influences of conservation tillage on SOC and N processes in China were: (1) strengthen the on-site studies on the mechanisms of conservation tillage effects on SOC sequestration and N use; (2) enhance the study of relationships between SOC and N and their interaction effect on soil fertility under conservation tillage; (3) link environmental protection, sustainable soil management, SOC sequestration and N use; and (4) deepen the study of conservation tillage effects on SOC sequestration and N use in macro-scale.