The determination of critical point in rheological-fractal models for most of the food gel systems and polyme viscoelastic systems are based on the point of 95% or 90% value of the storage modulus in linear viscoelastil region. It is not a precise method because the modulus during linear-nonlinear viscoelastic transition region an not always monotonous decreasing. Therefore, there is an urgent need for a more stable and precise approach 0 determine the critical point, making the scaling behavior calculation closer to the physical truth. This researcl studied on a typical food system, acid-induced peanut protein isolate (PPI) gel, trying to put forward a nay critical point for isotropy food gel and non-newton polymer systems. Result shows that when the increasini higher harmonic reaches a certain value, the corresponding strain could be regarded as a new critical strait point. The image of the microstructure captured by confocal laser scanning microscope (CLSM) was used ti calculate the actual fractal dimension, which was 2.3517. It was demonstrated that the fractal dimension cal culated from rheological fractal model using the new critical strain obtained from the Fourier transform analysi is closer to its actual value (2.3517).