High-temperature and high-pressure wells are facing a lot of problems such as complicated stress on the production string, severe deformation, and annular pressure, which seriously restrict the pace of drilling and development of HPHT oil and gas resources in China. In this paper, theoretical analysis and software calculation are combined to study the stress and deformation of an HTHP well string. Based on the research results, the authors have established an algorithm and method of mechanical analysis for high-temperature and high-pressure wells. The method could be effectively applied to drill string analysis in high-temperature and high-pressure well conditions. Lastly, the developed method of analysis and calculation algorythm has been verified for the actual production conditions. Based on the proposed calculation method, we have evaluated the force, deformation, and trap pressure values of the drilling string and packer under different working conditions. The results can be used to assess the safety of field operations. In this paper we provide the algorithm and method for production string analysis in HTHP wells.