Abstract: In accordance with the statistic characteristics of fatique cracking, a practical method has been put forward in this paper to deternxine fatique cracking constants of sucker rods.The constants deduced from this method are correlative with sucker rod survival probability,hence corresponding to the results from other metheds. The distribution law of fatique
cracking lifetime of sucker rods and the correlativity betweem C and m are slso tentatively discussed and tested in this paper.

Key words: Fatique cracking lifetime, Sucker rods, Statistic inference