Abstract: The critical pressure and the conditions of the rod and tubeoff-center wear were determined through the analysis of the sit-nation-forced of the rod strings of the pumping wells in the water-drive and the application of the bent and curved line differ-ential equation of the roll strings in this paper; the axial force and the axial pressure of the rod was determined with the wave e-
quation to turn the load picture to the pump dynamometer, and the diagnosis method of the and and tube off center wear of the pumping well in the water-drive was formed, using this method to diagnose whether or not the rod and tube is off-center wear and to diagnose the reasons, and to diagnose 107 oil wells .the diagnosis coincidence rate of the rod and tube off-center wear
was up to 84.3%，through the contrast and analysis of the 62 oil wells which used this method to treat the rod and tube off-cen-ter wear and has praluced about one check out pump cycle, the average check out pump cycle was prolonged 239 days.

Key words: water drive, off center wear, diagnosis, meth-od