Viscosupplementation treatment of osteoarthritis with sodium hyaluronate (HA) is prevalent in clinical practice but always associated with rapid degradation. Another natural polysaccharide chitosan (CS) has the potential to be used in viscosupplementation but is limited by the poor aqueous solubility. Herein, we formulated a viscosupplementation agent with a zwitterionic polymer modified chitosan (CS-CBAA), which featured with bottle-brush structure and poly(carboxybetaine acrylate) side chains. It was found that the incorporation of zwitterionic sidechains greatly enhanced chitosan's solubility up to approximately 130 mg/ml in solutions of pH 7.4. A gel-like behavior was also found in CS-CBAA solution due to intermolecular interactions between zwitterionic sidechains. Compared to HA, the viscosity of CS-CBAA solutions was obviously retained when subjected to hyaluronidase degradation tests. CS-CBAA was also approved comparable protection effect to cartilage and prior effect to ceramic materials. In a papain induced osteoarthritis mice model, CS-CBAA solutions of 120 mg/ml offered comparable cartilage protection to HA. This work presented a systematic study on a new viscosity supplement CS-CBAA, which exhibits exceptional lubricating properties and holds promise as a potential replacement for the current HA-based viscosity supplement in the treatment of early-stage OA.