Single- and multi-layer graphene was fabricated from expanded graphite by liquid-phase exfoliation method in organic solvents. Its morphology and structure were characterized. The effects of organic solvent, time and reductant on the electrical properties of graphene platelets were studied by four-point probe characterization method, and the preparation conditions of graphene optimized. The results show that graphene platelets have high electrical conductivity by using acetone as the dispersant, which can achieve 219.09 S/cm. The graphene exhibits good electrochemical performance compared with the expanded graphite, its specific capacitance reaches 18.8 F/g. In PBS buffer solution of pH=7, a sensitive stripping peak at 0.1 V to Pb2+ ion occurs, and the detection limit is 0.05 mmol/L.