Abstract: A method to improve the underwater object navigation accuracy for ROV is put forward.Unlike traditional ocean GPS position technologies,tug buoy is used.With the benefit of it,researchers needn't prepare the buoy array before ROV is to work,also the ROV can move faster and even much more far away.In this case,it is important to correct the distance between the buoy and the underwater ROV.Two routes are used to get it.And how to use IMU to get the distance is discussed in detail,the data fusing method which is used to improve the accuracy.An experiment system is given to examine this correction technology.