In this study, firstly, we compare various kinds of imitator robots and then by investigating of various fish robots properties, we design a mechanism and control circuit for a kind of these robots which its structure was inspired from knife fish. This robot has a segmental anal fin in its bottom which produces required force for advancement and maneuver. It consists of two servomotors and uses a kind of mechanical system to change direction and depth which is presented in this work. Another property of this robot is the existence of density control box for robot suspension which increases its capability for freight. The required signals are sent to this robot to produce the movement and maneuver by using a control handle and a wireless system which are installed on a control board. Therefore, it is possible to control the robot from out of the pool. In this paper, an electrical circuit is designed to control servomotors which enables us to control revolution, speed and phase differences of neighbor servomotors in fins. We also control two servomotors to regulate direction and depth.