The novel hydrophobic luminescent copolymer P(Ir-TFEMA) was developed as an online dissolved-oxygen (DO) sensor. The phosphorescent moiety of cyclometalated iridium(III) complex exhibits red emission near 650 nm with a large Stokes shift of about 245 nm and minimal optical interference from the fermentation system. The covalent incorporation of the chromophore into the polymeric matrix rather than physical doping was used to avoid phase-separation and leaching problems. The low molar ratio between the introduced chromophore and polymeric matrix within the range of 1:135-1:250 was confirmed to have little influence on the luminescence response ability. To assess its potential utility, this copolymer was applied to the online monitoring of DO during the cephalosporin C fermentation process. The screen-printing technique was utilized as a rapid and reliable automatic approach to preparing sensor films with good photostability and fatigue resistance, showing promise in bioprocess monitoring as a low-cost DO indicator for high-throughput microbioreactors.