Abstract: Farmland ecosystems are important for maintaining terrestrial ecosystems and environmental homeostasis. As farmland ecosystems develop and evolve, change information is stored in the environment such as in phytoliths, which are stable, non-crystalline minerals in the soil that can indicate climate change. Phytolith analysis has been used for agricultural archaeology, paleoclimate reconstruction, and for estimating biogeochemical cycles and global carbon sequestration potential. Crop cultivation has a long history, and crops are globally distributed. Therefore, studying crop phytoliths and phytolith-occluded carbon is useful for exploring the origin and development of agriculture, estimating farmland ecosystem carbon sequestration, and responding to global climate change. The content and distribution of phytolith-occluded carbon, the phytolith carbon sequestration potential, and the contribution to global carbon sequestrations were analyzed (by literature review and phytolith morphological and archaeological information) to determine future crop phytolith research directions. The results showed that crops had differing phytolith characteristics, and most crop phytolith research had been completed in the family Gramineae. The crop phytolith carbon content was correlated to crop's carbon sequestration capacity and efficiency, and the phytolith-occluded carbon content may also be affected by the growth environment and plant genotypes. The climate, surface vegetation, and soil environment of the ecosystem had direct and indirect effects on the regional phytolith carbon sequestration potential. Significant differences in carbon sequestration between farmland crops were observed. Applying a silicon fertilizer or a silicon-phosphorus compound fertilizer and planting crops with high silicon content can significantly improve the carbon sequestration potential. Future studies should investigate the phytolith carbon sequestration of specific crops to identify past carbon sequestration levels and compare them with the current potential. The plant migration law, root systems, and soil should be improved, and crop silicon levels should be analyzed to determine the effect on accumulation volume and carbon sequestration. Future studies should investigate the silicon absorption mechanism, root silicification process, and phytolith-occluded carbon content of crops and the agricultural carbon sequestration potential of the ecologically fragile karst area in Southwest China to improve farmland ecosystem crop planting and carbon sink estimation.