Dissolved oxygen (DO) plays a crucial role in environment, food processing, and biotechnology. Although several physical-doping DO probes have been developed, a sensitive and reliable sensor for real-time and noninvasive DO detection in bioprocess is still challenging. Here we demonstrate a morphology-tuning strategy to improve the sensitivity and responsiveness of DO polymeric sensors (P(Pt-TPP-TFE-Ad) and P(P(pt-TPP-TFE-POSS)) by decorating them with the same platinum(II) porphyrins and different morphology-tunable moieties in a supporting matrix. Experimental results show that the sensitivity and response of sensors increase with size effect of the morphology-tunable moiety because the bulky morphology-tunable moiety facilitates the formation of an interconnected and porous network that can promote oxygen permeability. Additionally, P(Pt-TPP-TFE-POSS) features excellent linear Stern-Volmer quenching, superior stability, and reversible response, thereby permitting the real-time and noninvasive quantification of DO during cephalosporin C fermentation. Our work offers an ideal tool for online sensing of DO in industrial and biological applications.