An electromechanical actuator (EMA) is the main component for the attitude control of robotic systems. This study focuses on solving the problems of a robot′s incapability in measuring small-size EMAs, inability to reflect the machine performance comprehensively, and single measurement item. According to the characteristics of small-size EMAs, a testing machine for the comprehensive performance test was developed to measure the transmission accuracy, electric parameters, and mechanical characteristic of small-size EMAs. The testing machine mainly comprises a precision mechanical system, control hardware system, and measurement and testing software. The testing machine adopts a horizontal structure. A special fixture is designed to satisfy the measurement requirements of different types of EMAs while ensuring the accuracy of the measurement system. The developed test software not only satisfies the comprehensive measurement of multiple performance indicators of small-size EMAs, but can also analyze the measured results. Test results show that the measuring machine operated stably, with a repeatable measurement deviation of less than 3%, thereby encompassing a wide range of small-size EMAs. The precision conforms to the design requirements, and the testing machine can yield automatic precision measurements. The development of the testing machine facilitates the establishment of an overall quality evaluation system for small-size EMAs.