The influence of friction pressure and time on morphological characteristics and mechanical property of the continuous drive friction welded joints of medium carbon steel 45(GB) was investigated in terms of the newly proposed two character factors, i.e. sticky length to diameter ratio α = length of welded zone / original diameter and scaling factor η = width of outer heat affected zone / width of center heat affected zone. The results show that, with the increase of friction pressure the sticky length to diameter ratio α increases firstly and then decreases, while the scaling factor η increases all along. However, by a friction pressure 60 MPa, the sticky length to diameter ratio α increases and the scaling factor η decreases continuously with the increasing friction time. When the integrative factor δ (δ=η/α) falls in a range 1.15-1.31, the mechanical property of joints is good because the heat input is moderate, which therefore can be used as a criterion of selection of welding parameters for gaining good performance of the continuous drive friction welded joints of the steel 45(GB).