Zwitterionic polymers are characterized by an equal number of positive and negative charges, resulting in an overall electrical neutrality. Attributed to their robust hydrating effect facilitated by electrostatic interactions with water molecules, zwitterionic polymers display notable resistance against nonspecific protein absorption, bacterial and platelet adhesion. Consequently, these polymers demonstrate outstanding antibiofouling properties, prompting widespread attention for their application in biomedical and engineering domains. This article provides an overview of the anti-biofouling mechanisms of zwitterionic polymers, focusing on hydration effects and spatial effects. Leveraging their anti-biofouling properties, zwitterionic polymers find application in the development of fouling-resistant coatings and antibacterial coatings for medical devices and biosensors. Additionally, owing to their anti-immune rejection properties and interfacial lubrication characteristics, these polymers have been employed in areas such as drug delivery, wound healing, and orthopedic materials. The paper reviews the progress in the application of zwitterionic polymers, analyzes existing challenges in practical implementation, and outlines the potential future prospects in their applications.