The invention discloses a method for measuring the low background carrier concentration in a semiconductor material device, and the method comprises the following steps: measuring the flat belt voltage on the surface of a region to be measured and the differential capacitance response under the optical excitation condition; establishing a numerical value model of the region to be measured and theadjacent region; and comparing the surface differential capacitance under the optical excitation condition of the region to be measured of the numerical value model and the practical measurement so as to determine the balanced carrier concentration. The method disclosed by the invention is suitable for the accurate measurement of the specific function region in the semiconductor material or device provided with a complicated structure, and the background carrier concentration of the specific function region is lower than 1015cm<-3>; and method can be used for detecting a single microcosmic block in an integrated or array device.