Abstract: Charging phenomena of oxides (such as Al₂O₃ and SiO₂, etc.) caused by the irradiation of incident electron beam have been reduced in an oxygen environmental scanning electron microscope (SEM) at the O₂ pressure of 5×10^-3 Pa to 2×10-²Pa. The desorption of stimulated oxygen in oxides makes the oxygen vacancies on the surface of sample become the charging potential trip so as to produce charging phenomenon. The charging phenomena on oxides have been compensated by repairing surface defects by the oxygen ions produced in the oxygen atmosphere. The oxygen environmental scanning electron microscopy is a simple and automatic regulated charging compensation method on insulating oxide materials. Al₂O₃ spectra of Auger electron spectroscope (AES) prove that the surface charging of the Al₂O₃ can be completely eliminated under the O₂ pressure of 6×10^-6Pa.