The accurate measurement of arterial blood oxygen partial pressure often plays an important role in the clinical assessment of patients with respiratory conditions such as an acute exacerbation of chronic obstructive pulmonary disease and acute lung injury/adult respiratory distress syndrome. An oxygen-sensitive fluorescence indicator with high biocompatibility was synthesized and then fabricated to the end of an optical fiber. The properties and accuracy of this oxygen sensor were investigated in vitro using physiologic solutions under varying conditions or human blood, and in vivo by obtaining measurements after inserting this optical sensor into the collateral circulation system of rabbits. The sensitivity of the oxygen sensor was relatively stable during altered conditions of pH, P(CO2), osmolality, and protein concentration in solutions and during alterations of oxygen and nitrogen content in human blood. There was a linear correlation between the reciprocal value of the fluorescence intensity and Pa(O2) in both in vivo and in vitro experiments (animal arterial circulation and human blood). Our results suggest that this oxygen-sensitive fluorescence indicator, which has a high biocompatibility, may have the potential for use in real-time monitoring of blood oxygen partial pressure in various clinical settings.