Length of the femoral stem is reduced to prevent loosening and to preserve bone stock for potential revision surgery. However, the influence of the stem shortening on primary stability and weight bearing is not investigated enough from a dynamic viewpoint. In the present paper, we report primary stabilities of five femoral stems with different length based on clinical Total Hip Arthroplasty (THA) data. The length was based on standard type of tapered wedge-shaped cementless stem, defined as 100% of the stem length. Furthermore, comparison of femoral stems having 75%, 50%, 40% and 30% of the stem length was made. The subject was ten female patients operated for THA. Finite Element model implanted with five lengths of the femoral stem was loaded by forces representing two physiological activities: walking and stair climbing. In conclusion, when the stem length became less than 40%, the primary stability of the stem decreased. These results, suggested that excessive stem shortening had an influence on the weight bearing.