This study was conducted to investigate the effect of Hbs on accuracy of pulse oximetry in blood oxygen saturation level measurement among adult patients with sickle cell disease crises in Shahid Mohammadi Hospital of Bandar Abbas during 2017. For this cross-sectional study, the statistical population included all patients with sickle cell disease who were hospitalizes in emergency department of Shahid Mohammadi Hospital of Bandar Abbas during the second half of 2017. At first, pulse oximetry was performed on subjects and then the arterial blood samples were taken to analyze arterial blood gas (ABG) according to the protocol. Blood samples were taken from each subject for electrophoresis and determination of Hbs level. The mean results of pulse oximetry on patients was 97.69 ± 1.57, with the lowest 90% and the highest 98%. In contrast, the oxygen content of the ABG analysis varied from 78 to 93%, and the mean of these results was 87.54 ± 3.54. The Hbs level of electrophoresis on patients was 72.78 ± 8.12%. The difference between the blood oxygen saturation level in the blood obtained by pulse oximetry and arterial blood gas analysis was less than 10%. The findings showed that the oxygen saturation level in the blood measured by using two techniques of pulse oximetry and AGB analysis was significantly different. It is advisable to use more accurate techniques to estimate the oxygen saturation level in the blood and to determine the rate of hypoxia.