Several experiments were carried out to investigate the effects of water to binder ratio(w/b) and mineral admixtures on water sorptivity and permeability of new-old concrete composite system in this paper in order to further understand the transport properties and thus degradation mechanism of new-old concrete repair system. Results indicate that a reasonable choice of w/b of new concrete is of great importance for obtaining new-old concrete composite with a low water sorptivity. Addition of ultrafine powder such as silica fume as one of component of repairing materials will benefit for effectively reducing water sorptivity and permeability of new-old concrete repair system in practice. The linear correlative coefficient between capillary sorption coefficient, coulomb electricity and porosity of new-old concrete composite sample is bad and lower compared with those of corresponding new concrete samples. The total porosity of new-old concrete composite sample is not an exclusive factor determined its water sorptivity and permeability. The pore structure of new-old concrete composite sample, especially interfacial transition zone between new and old concrete plays more important role on transport properties of sample.