ABSTRACT This study investigated the solution conformation, microstructure, and rheological properties of a quaternary ammonium salt of sodium carboxymethyl cellulose (NaCMC) in aqueous solution. The results showed that the chain conformation of NaCMC exists in the form of linear aggregation of semi‐flexible coils. NaCMC aqueous solution is a typical non‐Newtonian fluid and can show shear‐thinning behavior. Its viscosity increases with the increase of concentration (1.0%–3.0%, w/v) but decreases with the increase of temperature (5°C–50°C). The flow curve conformed with the Cross model fitting. The thixotropy index exhibited strong thixotropic behavior with the increase of concentration; the viscoelastic properties showed oscillatory behaviors between a dilute solution and an elastic gel, which exhibited random coil conformation with the potential to form a weak gel‐like network. In addition, the viscosity at high concentrations (2.0%, 2.5%, 3.0%, w/v) and low temperatures (5°C, 15°C, 25°C) almost conformed to the Cox‐Merz rule, and NaCMC rheological properties are highly dependent on changes in concentration and temperature. Investigating the effects of concentration and temperature on the rheological properties of NaCMC can help us better understand its molecular behavior, providing theoretical support and optimization strategies for applications in drug delivery, food processing and packaging, cosmetics, and other fields.