Abstract: Full-liquid pig manure typically exhibits high total solids (TS) content and complex non-Newtonian flow behavior, which substantially affect the mechanical applicability, transport energy demand, and uniformity of land application. These rheological constraints often hinder the efficiency of manure handling systems, particularly in cold regions where low temperatures exacerbate flow resistance. To address the limitations of traditional analysis and the lack of systematic parameter optimization, this study adopted a stepwise experimental strategy combining single-factor experiments with Response Surface Methodology (RSM) to quantitatively investigate rheological mechanisms and optimize transport parameters. First, single-factor experiments were conducted using TS levels ranging from 0.24% to 15.29%, temperatures from 5 ℃ to 35 ℃, and shear rates from 2 to 600 s^-1. Steady-state rheological tests confirmed that pig manure is a typical pseudoplastic fluid. TS was identified as the dominant factor affecting apparent viscosity, with a critical threshold observed at 4.28% TS, marking the transition from weakly non-Newtonian to strongly shear-thinning behavior. Furthermore, a critical shear rate of approximately 158 s^-1 was determined based on the rheological curves; beyond this threshold, the flocculent structure of the fluid was fully disrupted, and viscosity approached a stable limit (<10 mPa·s). Building on these preliminary findings, a three-factor, three-level Box-Behnken Design (BBD) was employed to optimize the process specifically for challenging engineering conditions (High TS >10%, Low Temperature 5-15 ℃). A log-transformed quadratic regression model was constructed to accurately predict apparent viscosity. Contrary to previous single-factor observations where temperature effects appeared negligible, the RSM analysis revealed significant main effects of temperature (P<0.01) and a significant interaction between TS and temperature (P< 0.05). The study elucidated a strong concentration-dependent thermal sensitivity: while temperature had minimal effect at low TS, the coupling of low temperature (5 ℃) and high TS (>10%) triggered a "low-temperature locking effect." This phenomenon caused an exponential increase in viscosity due to reduced molecular thermal motion and enhanced hydrogen bonding networks among solid particles. To minimize transport energy consumption while ensuring efficient nutrient loading, numerical optimization was performed under winter operating constraints. The optimal parameters were identified as: TS of 10.0%, temperature of 15.0 ℃, and shear rate of 136.1 s^-1. The model's reliability was confirmed by validation experiments, which showed a relative error of less than 5% between predicted and measured values. Notably, the optimized shear rate (136.1 s^-1) is lower than the critical value (158 s^-1), indicating that ideal viscosity reduction can be achieved at an energy-efficiency inflection point without pursuing excessive rotational speeds. In conclusion, this study quantitatively clarifies the synergistic effects of TS, temperature, and shear rate on manure rheology. The validated model provides a theoretical basis for the precise matching of pump power and mixer design to prevent dead zones. Crucially, it suggests that for winter transport of high-solids manure, implementing heat tracing (maintaining ≥15 ℃) is a more energy-efficient strategy than solely increasing pumping power to overcome the "low-temperature, high-solid" viscosity barrier.