Projection-to-plane model of the Steering linkage has low accuracy. Multi-body dynamics model is inconvenient to use complex optimization algorithm. To deal with these difficult problems, a spatial structural nonlinear modeling of the steering linkage in an 8×4 type heavy duty truck was developed using the rotation vector method of the spatial RSSR four-rod mechanism. The steering-wheel angle was the model input, and the steering wheel deflection was the model output. The steering linkage was broken up into six spatial RSSR four-rod mechanisms according to the angular displacement transfer path. Through establishing each RSSR mechanism model and then integrating them, the angle relationship between the steering-wheel and steering wheels was acquired. The simulation and test results showed that the Ackerman deflection errors of the right steering wheels of the first and second steering axles reduced 50% and 28.6% respectively in the spatial model comparing with the projection-to-plane model. The results also showed that the maximal deflection error of the spatial model in all the steering wheels was 1.8° relative to the test results, while the error of the projection-to-plane model was 3.9°. In the whole steering-wheel angle, the spatial model had high accuracy. The spatial model described the mathematical relationship of each moving component in the steering linkage distinctly. The model may provide theoretical foundation for analyzing the moving interaction between the suspension and steering linkage and the optimal design of the steering linkage.