In this paper, the preparation of sensor membrane and preconcentration and detection of cadmium ions (Cd²⁺) was implemented by combining porphyrin and membrane technology. The polysulfone/porphyrin functional membrane was prepared by loading 5,10,15,20-tetrakis(4-N-methylpyridyl)porphyrin p-toluenesulfonate (TMPyP) on the surface of polysulfone (PSF) membrane which was modified with poly(sodium p-styrenesulfonate) (PNaSS) brushes. Under the dynamic condition, the functional membrane shows good preconcentration property for Cd²⁺ due to the coordination interaction between TMPyP and Cd²⁺. The spectral and the apparent color changes enable the detection function of the membrane and the reversible coordination endows the membrane with good regeneration ability. Lower initial concentration of Cd²⁺ solution and lower flow rate lead to lower absorption and detection rate of the functional membrane. The preconcentration and detection for ultratrace Cd²⁺ can be achieved by controlling the capacity of TMPyP. Compared with the static adsorption, the function membrane shows faster detection for Cd²⁺ under the dynamic condition which favor the diffusion and adsorption of Cd²⁺ on the membrane surface.