Dispersing atomic metals on substrates provides an ideal method to maximize metal utilization efficiency, which is important for the production of cost-effective catalysts and the atomic-level control of the electronic structure. However, due to the high surface energy, individual single atoms tend to migrate and aggregate into nanoparticles during preparation and catalytic operation. In the past few years, various synthetic strategies based on ultrafast thermal activation toward the effective preparation of single-atom catalysts (SACs) have emerged, which could effectively solve the aggregation issue. Here, we highlight and summarize the latest developments in various ultrafast synthetic strategy with rapid energy input by heating shockwave and instant quenching for the synthesis of SACs, including Joule heating, microwave heating, solid-phase laser irradiation, flame-assisted method, arc-discharge method and so on, with special emphasis on how to achieve the uniform dispersion of single metal atoms at high metal loadings as well as the suitability for scalable production. Finally, we point out the advantages and disadvantages of the ultrafast heating strategies as well as the trends and challenges of future developments.