Sound navigation and ranging, SONAR is applicable in underwater positioning systems. In these systems, sound, which propagates in the water with minimum attenuation, is used. Generally, sonar systems divide into two groups: active and passive. In active sonar systems, transmitted sound wave from antenna, transducer, after incident the target will be received to the transducer. Control subsystem of an active sonar is responsible for reading the input keys (keyboard), storing the state of them, synchronization of sending and receiving signals, and observation of all activities of a sonar system. In this article, control subsystem of an active sonar using microcontrollers is designed and implemented. A microcontroller is a kind of microprocessors, with internal RAM, EEPROM, I/O ports, and timer. In application with minimum space and cost, microcontrollers usually are used. Three important criteria for selecting one kind of microcontroller are: 1- satisfying our necessities. 2- existence of software resources such as compilers, assemblers. 3- Existence of microcontroller handbooks. Regarding these items, 87Cc51 microcontroller of Intel Company is selected for this project. 87c51 is an eight-bit microcontroller which is optimized for control applications. Control operation in an active sonar looks like the brain in the human body. It synchronizes all parts of the sonar to each other. For doing this duty, it generates some control signals for transmitter, receiver, driver of motor, and display sections of sonar system. In addition, feedback signals from other parts enter as inputs to the control system. In the complete version of this article, first, an introduction and history of sonar systems in the world will be presented. Second, microcontrollers in general will be discussed. Finally, control subsystem for active sonar system based on microcontrollers will be introduced.