Abstract: In sucker-rod oil pumping system, the sucker rod is its vulnerable spot. The paper gives a detailed analysis of the design method causing rod string dropout and points out its inadequacies. By analyzing main causes of rod string dropout and taking the measure of comprehensive treatment, the rod string dropout rate in Zhoucheng Oilfield was lower about 10% in 2003 than from 2000 to 2002 and the inputoutput ratio was 1:3. The recommendation about anti-dropout of rod string in Zhoucheng Oilfield is also presented in the paper.