Supersonic chemical oxygen iodine laser is a complex process including flow, chemical reactions and lasing. In process of power extraction, output of laser has a direct influence on flow fields and species, which will affect beam quality and power of lasers. Influence of power extraction on inner flow field of the laser has been numerically investigated based on computational fluid dynamic coupling procedures of paraxial wave function. Numerical results show that as power extraction process takes place, consumption of singlet delta oxygen is enhanced since pumping reaction is accelerated, concentration of iodine molecule is elevated, and changing direction of intracavity temperature via power extraction process depends on extraction efficiency. Intracavity temperature arises in high extraction efficiency cases and decreases in low extraction efficiency cases. Computational method in this paper provides an effective tool for research and development of chemical oxygen iodine lasers.