Abstract：For the purpose of accurately measuring nanoparticle size by scanning electron microscope(SEM) method, SEM magnification calibration method and micrometers spacing measurement method were developed. SEM digital images of micrometers were firstly captured and obtained, and MATLAB software was used to convert digital images into grayscale images automatically, and then the brightness data of grayscale images could be obtained. Based on this work, after the determination of the top line, baseline, the bottom line position of peak structure in the grayscale images, centroid position could be accurately obtained and the potential error of imaging and data processing could be effectively eliminated. The average micrometers spacing were calculated by using the centroid algorithm, and finally, the calibration coefficient and calibration error of SEM magnification could be calculated by comparing with the certified value of micrometer spacing. The reliability of the SEM calibration results were verified by measuring a particle size certified reference materials(CRMs) using calibrated SEM, and a consistent results finally be obtained with the certified value of CRMs. So from the result, a conclusion can be drawn that our developed SEM magnification calibration method and micrometers spacing measurement method are effective and reliable, which can effectively avoid the influence of poor image quality and artificial factors on the measurement results to obtain accurate particle size results.

Keywords: scanning electron microscope; magnification; calibration; centroid method; particle size