The work aims to investigate precise quantification methods for weight distribution in truck loading balance, with the objective of providing guidance for practical cargo loading operations. Focusing on a certain brand of truck under standard load, a balance equation was established through mechanical analysis, and a mathematical model with the optimization objectives of optimal axle load distribution and minimizing the bending moment of the carriage was established, and constraints such as the allowable bending moment of the carriage, load transfer ratio (LTR), and average density of goods were incorporated. An improved simulated annealing algorithm was adopted for iterative optimization to search for the optimal loading layout, and Matlab software was used to draw a three-dimensional load distribution map. According to the three-dimensional load distribution map, the loading plan generated by a certain loading platform was optimized, with an axle load ratio of 0.387 3, which was closer to the ideal axle load ratio than the original plan. At the same time, the peak bending moment of the carriage was also reduced to 4 579. The overall performance was that the distribution of the total center of gravity of the goods was more reasonable, and the bending moment and shear force diagrams were smoother, indicating a significant improvement in the vehicle's load state. In conclusion, the method of constructing a three-dimensional load distribution map considering the axle load ratio and bending moment extreme values can solve the problem of precise distribution of cargo weight in specific truck loading scenarios, optimize the vehicle's load balance, and reduce safety hazards. Example verification proves that the method can be used to generate loading guidance maps and adjust the loading layout, which has guiding values for actual loading operations.