Background: Implant loosening is one of the most common problems occurring after total hip replacement. Important factors, such as geometrical characteristics of the implant, quality of bone tissue, implantation process, and age and lifestyle of the patient, affect the loosening. This study aims to analyze the dynamic stress and strain on the bone-implant interface in the stance phase of normal walking. Methods: A two-dimensional model, including a femur and its artificial joint, was used for numerical simulation in ADINA software using the finite element method. Young's modulus was assumed to be 12 GPa for the bone and 210 GPa for the medical stainless steel implants. At the bone-implant interface, the coefficient of friction was assumed to be 0.22, and the model simulated the conditions of a cementless surgery. The load applied to the replaced joint head was dynamically consistent with the normal walking cycle of an individual weighing 75 kg. Results: The results showed that the strain difference is maximal at the end stem regions of the interface. The strain difference was 1.6% at the inner edge, being 16 times that at the outer edge of the interface. The maximum stress reached about 5.7 MPa. Conclusion: The largest strain difference occurred in the lowest area of the implant stem, which indicates the possible location of the implant loosening. This information can also be important in employing hip replacement surgery strategies and developing optimal mechanical designs of the artificial joint. Keywords: Total hip replacement, prosthesis loosening, computer simulation, finite element analysis, gait Received: 4 months before printing; Accepted: 10 days before printing