In the electro-photography system, the photoconductive materials are charged by either the corona devices or the primary charge rollers. Unlike the corona device, the primary charge roller does not pollute the air, so it is commonly used to charge the photoconductive material in the low speed printing nowadays.Traditionally, the measurement of the PCR resistance is used to detect the charging ability of the PCR and determine the quality of the PCR.A new automatic primary charge roller detecting system is introduced in this paper. A high voltage needle tip is used to ionize the air around the PCR. The PCR is charged and discharged under high frequency, the response voltage in the PCR then undergoes the conditioning process where the signal is amplified and the noise are filtered. The signal is then accessed by the high-speed data acquisition interface. A graphic user interface is to display the charging and discharging curve of the PCR test specimen. These curves can be compared with the standard charge and discharge curve of the standard PCR, to determine whether the test specimen is “go” or “not go”. The detection process is easy and time saving.