Space inertial actuators, represented by reaction wheels, momentum wheels, flywheels, and control moment gyroscopes, are indispensable angular-momentum exchange devices in spacecraft attitude determination and control systems. Owing to their non-consumable operation, high reliability, and precise torque-generation capability, these actuators are widely employed for attitude stabilization, rapid attitude maneuvering, payload disturbance mitigation, and precision pointing in modern satellites and space vehicles. With the rapid growth of high-resolution Earth observation missions, deep-space exploration programs, and large-scale commercial satellite constellations, the performance requirements imposed on inertial actuators are becoming increasingly stringent. This paper systematically reviews the current state of the art in space inertial actuator technologies by integrating peer-reviewed research with publicly available industrial product information, and summarizes recent research progress, representative products, and development strategies in the United States, Europe, Russia, and China. By comparing the technical characteristics and evolutionary pathways of mainstream reaction wheel, momentum wheel, flywheel, and control moment gyroscope systems, the study identifies the principal technological drivers shaping future development. The analysis reveals five dominant trends: extended operational lifetime, higher control accuracy, greater torque and angular-momentum density, reduced micro-vibration disturbance, and scalable, cost-effective manufacturing. These findings provide a systematic technical reference for future research, engineering design, and industrial development of advanced space inertial actuator systems in China and internationally, particularly for next-generation spacecraft requiring long service life, high pointing accuracy, low disturbance, and scalable production.