Used ultrasonic network to realize the location of the robot working under water coal slurry is an available means.A serial communication system is designed in base of the precision of location and the system reliability.The upper machine is industrial control computer and the under machine is single chip micyoco（SCM）.The industrial control computer is mostly to calculate the position of the robot

and the SCM is mostly to measure the distance.The three points location theory is used to calculate the position of the robot.The result of experimentation shows that this system works steadily

and the calculation method for location is available.