A novel sodium alginate hydrogel composite membrane (U-MCM-41@ASA) was successfully prepared using 3-aminopropyltrimethoxysilane functionalized sodium alginate (ASA) with 3-urea-propyltrimethoxysilane functionalized MCM-41 molecular sieve (U-MCM-41) for the highly efficient adsorption of Pb2+. The incorporation of functionalized MCM-41 into the sodium alginate hydrogel network significantly increased the amount of active adsorption sites and enhanced the adsorption performance of the composite membrane. A variety of characterization techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS), were used to systematically analyze the microstructure, surface morphology, functional groups, surface chemical states, and thermal stability of the U-MCM-41@ASA composite membrane. The results indicated that U-MCM-41 was uniformly dispersed within the sodium alginate matrix, and the surface was rich in active groups such as amino groups, providing abundant adsorption sites for Pb2+. The removal of Pb2+ from aqueous solution by the U-MCM-41@ASA composite membrane was primarily achieved through coordination and chelation between the organic functional groups on the membrane surface and Pb2+, as well as electrostatic adsorption and ion exchange. Adsorption kinetics and thermodynamics analyses revealed that the adsorption process conformed to the pseudo-second-order kinetic model and the Langmuir isotherm model, and it was a spontaneous, endothermic, entropy-increasing behavior. Under the adsorption conditions of 15 mg composite membrane dosage, solution pH of 5.5, adsorption temperature of 45℃, initial Pb2+ concentration of 200 mg/L, and adsorption time of 240 min, the maximum adsorption capacity of the U-MCM-41@ASA composite membrane for Pb2+ reached 266.67 mg/g. Furthermore, the composite membrane exhibited excellent regeneration capability, with only a 10% decrease in adsorption capacity after five consecutive adsorption-desorption cycles. The U-MCM-41@ASA composite membrane not only possesses favorable adsorption performance and remarkable regeneration ability, but also offers advantages such as simple preparation and environmental friendliness, demonstrating potential application prospects in the treatment of lead-containing wastewater.