This paper presents a technique for single-cell electrical property (specific membrane capacitance and cytoplasm conductivity) characterization at a speed of 5-10 cells/s (vs. minutes/cell using existing techniques such as patch clamping and electrorotation). When a cell flows through a microfluidic constriction channel which is marginally smaller than the diameter of tested cells, electrical impedance at multiple frequencies is measured. Electrical and geometrical models are developed to interpret the impedance data and to determine the specific membrane capacitance and cytoplasm conductivity of individual cells. Results from testing 3249 AML-2 cells and 3398 HL-60 cells reveal different specific membrane capacitance and cytoplasm conductivity values between AML-2 (12.0±1.44 mF/m², 0.62±0.10 S/m) and HL-60 (14.5±1.75 mF/m², 0.76±0.12 S/m) cells. The results also demonstrate that the quantification of specific membrane capacitance and cytoplasm conductivity can enhance cell classification results since these parameters contain information additional to cell size.