The threshold shear rate (gamma(c1)) for producing a transient periodic structure ina film of the lyotropic liquid crystalline polymer poly(gamma-benzyl L-glutamate) in dioxane/nitrobenzene decreases with increasing molecular weight (MW). gamma(c1) proportional to MW(-a), where a is larger than 3. A high molecular weight and the consequent high anisotropy of the polymer favor the appearance of the transient periodic structure from both an energetic and dynamic point of view. The critical shear strain (gamma(c)) is ah increasing function of and proportional to the MW. The scaling rule for the appearance of the periodic structure, as well as the damped oscillation of viscosity in transient now, can be attributed to the liquid crystal polymer tumbling behavior.