The liquid-solid transition of low acyl gellan (LA) and sodium caseinate (SC) mixtures were investigated by using rheological measurements. The liquid-solid transition temperatures were determined from two criteria: the crossover of storage modulus G′ and loss modulus G″, and the Winter’s criterion. The results showed that the Winter’s criterion was more suitable to determine the sol-gel transition temperature. For LA/SC mixtures, there was a critical SC concentration (0.005g/mL ratio of mass to volume). The concentration of sodium caseinate almost had no influence on the gelation temperature of LA/SC mixtures at or below concentration of 0.005g/mL. While above 0.005g/mL, the gelation temperatures of LA/SC mixtures were decreased linearly with the increase of SC concentration. The relaxation critical exponent n can be determined by the Winter’s criterion. There was no universal n for the gelation in LA/SC mixed solutions, indicating that this gelation belonged to the cross-linking of existing macromolecules. And n increased with the increase of SC concentration until SC concentration reached a critical level, after which further increase in SC concentration resulted in a reduction of n. The fractal dimension df was calculated from n without the screened hydrodynamic interaction or the excluded volume effect and the trend of the change of the df was opposite to that of n. Using a non-isothermal kinetics model, active energy (Ea) during gelation was calculated. However, a discontinuity was observed in the activation energy plots. Based on this, two gelation mechanisms were presumed-association of low acyl gellan gum and sodium caseinate molecules and aggregation of polymer strands.