The novel grouting coupler was developed using seamless steel pipe through cold rolling press to reduce the cost of rebars splicing used in precast connection. Based on incremental tension test, the confinement mechanism and distribution of confining stress in the sleeve were studied. It is shown that the ultimate strength of this new splice can meet the regulation specified in JGJ107—2010. The initial confining stresses caused during the hardening process of the infilled grout are related to the mechanical properties of the spliced bars, grout and sleeve and dimensions of the splice. When these parameters are determined, the confining stress increased linearly with the increment of free expansion rate of the grout. The average confining stress in the deformed part is greater than it in the smooth part. For the deformed part, the confinement is mainly provided by the radial component of the interaction between the concentric ribs and the infilled grout. On the other hand, the confining stress in the smooth part is controlled by the dilation of the inner grout.