Transportable optical clocks are divided into three categories: high?precision transportable optical clocks, portable optical clocks, and balanced optical clocks. The working principles and research progress of these three types of transportable optical clocks are introduced, and their performance advantages and development limitations are analyzed from the perspectives of stability, uncertainty, and system integration. On this basis, the application prospect of transportable optical clock in mobile time service, geodesy, space exploration, micro positioning and other scenarios is prospected. It is proposed that the mobile performance of the high?precision transportable optical clock system should be improved by reducing the environmental sensitivity of the core laser components and improving the robustness of the laser components and vacuum system, the long?term stability of portable optical clocks should be improved by combining vacuum technology, artificial intelligence and other means, and the accuracy of the balanced portable optical clock should be further improved through the iteration of experimental schemes.