For a multi-dimension force transducer, the mutual coupling between any two force transducers is unavoidable, and normally, the coupling characteristic is nonlinear. But the nonlinear coupled transducers are often treated as linear coupled ones since the difficulty of nonlinear decoupling. The 6-axis wheel force transducer (WFT), as the key instrument of vehicle roadway test system, the precision of which is influenced badly by the mutual coupling. The linear coupling analysis and decoupling method was introduced, on the basis of which, the polynomial nonlinear coupling model was derived, and the polynomial nonlinear decoupling method was discussed. The measurement data of WFT were processed. The results indicate that the accuracy of nonlinear decoupling is higher than that of linear decoupling.