Controllability refers to the ability of an aircraft to quickly and smoothly complete required flight tasks. This paper proposes a controllability assessment method for the full flight envelope of supersonic transport (SST) aircraft, based on the control efficiency requirements in tentative airworthiness standards for supersonic transports (TASST) and flying qualities of piloted aircraft. First, configuration characteristics of SST aircraft and its differences from conventional layout aircraft were summarized. Second, some control efficiency assessment tasks were selected from airworthiness regulations, and the qualitative assessment tasks in airworthiness regulations were quantified with reference to flying quality specification. Finally, a quantitative analysis of the three-axis control efficiency of an sample SST aircraft was conducted under typical flight conditions, and the maximum control efficiency requirements for each axis were determined.