In this study, we report a method to generate a reliable and homogeneous brush-shape air plasma plume at atmospheric pressure for surface modification of PET polymers and biomedical applications. The room-temperature air plasma plume consists of well-aligned and stable microplasma jets formed in the vicinity of the ends of hollow optical fibers at atmospheric pressure. This plasma plume may lead to the uniform and large-area surface modification of PET polymers. The plasma plume may efficiently prevent the heat-sensitive polymers from being damaged and significantly affect the surface properties of treated polymers, such as surface chemical compositions, hydrophobicity and biocompatibility. Compared to a high density of blood platelets adhering onto the untreated PET sample, no adhesion of blood platelets is observed on the plasma-activated PET sample due to the surface functionalization. The reaction processes of plasma-activated species at the surface of treated polymers are discussed based on the obtained experimental results.