Efficient photocatalysis and electrocatalysis in energy conversion have been important strategies to alleviate energy crises and environmental issues. In recent years, with the rapid development of emerging catalysts, significant progress has been made in photocatalysis for converting solar energy into chemical energy and electrocatalysis for converting electrical energy into chemical energy. However, their selectivity and efficiency of the products are poor. Rare earth (RE) can achieve atomic level fine regulation of catalysts and play an crucial role in optimizing catalyst performance by their unique electronic and orbital structures. However, there is a lack of systematic review on the atomic interface regulation mechanism of RE and their role in energy conversion processes. Single atom catalysts (SACs) provide clear active sites and 100% atomic utilization, which is conducive to exploring the regulatory mechanisms of RE. Therefore, this review mainly takes atomic level doped RE as an example to review and discuss the atomic interface regulation role of RE elements in energy conversion. Firstly, a brief introduction was given to the synthesis strategies that can effectively exert the atomic interface regulation effect of RE, with a focus on the atomic interface regulation mechanism of RE. Meanwhile, the regulatory mechanisms of RE atoms have been systematically summarized in various energy conversion applications. Finally, the challenges faced by RE in energy conversion, as well as future research directions and prospects, were pointed out.