The object of this paper is to make clear the shear transfer mechanism and the shear displacement behavior in the connection of Half Precast RC member. The experiment and the 2-D non-liner finite element analysis were performed on the RC beam with horizontal joint. The study for five specimens whose parameters were joint steel bars and concrete shear-key was carried out. The results are as followed. The influence of shear resistance elements was examined based on our several experimental studies. The shear transfer mechanism and the shear displacement behavior at the interface can be explained by the author's model of shearing force - shear displacement relationship in connection of precast concrete.