Abstract: Climate smart agriculture (CSA) is the current agricultural development trend for countries around the world to address the dual challenges of climate change and food security, the core of which lies in the pursuit of Pareto optimality in the three dimensions of “Productivity & Income - Climate Adaptation - Emission Mitigation”. Evaluating the development level of CSA is essential for guiding sustainable agricultural practices, particularly in China, where agriculture plays a pivotal role in national food security and rural livelihoods. Based on the theory of complex system collaboration, this study constructed an assessment framework for the development level of CSA around the above three dimensions, and quantitatively evaluated the development levels of CSA in each dimension and the climate smart index (CSI) in China’s major grain producing areas from 2013 to 2022. And analyze the synergy and trade-off relationships among multiple objectives in each dimension. The results show that: 1) the CSI of the China’s major grain producing areas increased from 0.052 to 0.403 from 2013 to 2022, which is at a lower level but with an upward trend, and the scores of the three dimensions of the CSA increased from 0.150, 0.119, and 0.110 to 0.624, 0.589, and 0.568 respectively, with fluctuating characteristics in line with the trend of the CSI. The score of Productivity & Income is generally higher than Climate Adaptation and Emission Mitigation, indicating that major grain producing areas are in the initial stage of CSA development. 2) The development level of CSA in the China’s major grain producing areas shows significant spatial non-equilibrium, with the spatial pattern moving from dispersal to agglomeration, the regional gap gradually narrowing. The major grain producing areas in North, Northeast, and Central China gradually forming contiguous Climate smart areas. The development trend of the three dimensions of the three dimensions of the majority of the provinces has a consistent trend, with the level of development increasing year by year. 3) The correlation between multiple objectives under the three dimensions of CSA is dominated by synergy, meaning advancements in one dimension often benefit others. The degree of synergy of multiple objectives affects the balance of the development of the three dimensions and the overall development level of CSA. Among the objectives, “Agricultural economic resilience - Ecological carbon sink” has the strongest synergy, while the objective “Food production capacity - Ecological carbon sink” shows a significant trade-off, and the correlation between the other objectives has its own regional characteristics. To accelerate CSA adoption, this study proposes phased technology adaptation prioritizing region-specific innovations, differentiated policy interventions tailoring support mechanisms based on regional disparities, and synergistic objective management optimizing trade-offs, such as integrating agroecology with precision farming. The study offers a novel assessment framework for CSA development, facilitating more nuanced evaluations of agricultural sustainability, and by identifying key synergies and trade-offs, it provides actionable insights for mitigating multidimensional conflicts in CSA implementation, supporting China’s agricultural green transformation and food security strategies in the face of climate change, while also serving as a reference for other developing economies grappling with similar challenges.