Objective To propose some detailed methods for diagnosis of fractured stem failure in clinic by studying the mechanical mechanism of fractured stem failure and the specific causes of fracture occurrence after the total hip arthroplasty (THA). Methods The correlations between fracture stem failure and production, clinical situation and patients were analyzed by 2D and 3D finite element analysis (FEA) method to study the biomechanical mechanism of fracture processes. Results The reasoning route for fractured stem failure analysis after THA was proposed, and mechanical analysis and validation on fractured stem failure were conducted by FEA methods successfully. Conclusions Fracture should not occur on the artificial stem, for those that gone through the strength design and experimental test; statistical analysis on fractured stem failure showed that the occurrence of such fractured stem is a kind of little probability random event, which could be induced by a variety of non-normal factors, such as fluctuations in product quality, technical errors in clinic, patient accidents and so on. Strict controls on these factors can reduce the fractured stem occurrence; the reasoning route for fractured stem failure can help to discover the reasons of failure occurrence; the mechanical mechanism of specific fracture stem occurrence can be detected by 2D and 3D FEA methods.