AbstractAt present, the physical properties of hydrocolloids limit their wide application in food industry. To improve the viscoelasticity of sodium carboxymethyl cellulose (CMC) and sodium alginate (SA), cellulose nanocrystals (CNCs) were added into CMC and SA solutions to regulate the non‐Newtonian flow behaviors of composite systems under different conditions. The rheological properties of CMC/CNCs or SA/CNCs composite systems were studied using steady rheological measurements, dynamic rheological measurements, and creep compliance experiments. It was found that the viscosities and elastic modulus of CMC were positively related to CNCs concentrations in acid, neutral or alkaline environments. When the CNCs content was higher than 5% at pH 9.45, the gelation of CMC was accelerated, and the gelation strength was increased. The damping factor of SA decreased with increasing calcium ions contents. When calcium ions content was higher than 0.07%, the damping factor of SA was less than 1, indicating that SA system achieved gel transformation. The effect of CNCs on the apparent viscosity, shear stress, and storage modulus of CMC was more obvious in comparison to that of SA. Overall, as a rheology modifier, CNCs can minimize the contents of food colloids in any functional fluid while maintaining the thickening rheology.