Abstract: Research on unsymmetrical aerodynamic derivatives of an axisymmetric spinning cone was conducted, the aerodynamic parameter identification results of wind tunnel free-flight tests of a spinning blunt cone at Mach 6 were analyzed using biplanar optical system, and two angular motion equations were adopted for symmetrical and unsymmetrical aerodynamic derivative coefficients respectively. Comparing the coincidence degree between fitting curves and raw data, it can be found that the fitting curves of equations with unsymmetrical aerodynamic derivatives is better agreed with raw data, than the curves with symmetry assumption. That proves the presence of unsymmetrical aerodynamic derivatives for the axisymmetric spinning vehicle in hypersonic flow, similar to that in supersonic flow. Analysis shows dynamic derivative and Magnus moment derivative are both unsymmetrical between the in-plane and out-plane components, only the static derivative is in good agreement with symmetry assumption. The unsymmetry of dynamic derivative is considerably severe. So the dynamic derivative in only one component cannot predict the dynamic stability exactly, the other component is also indispensable, espectcally the unsymmetrical dynamic derivative. Furthermore, the dynamic derivative predicted by symmetry assumption would be much higher than the true value for one component, and much lower for the other component. Further investigation shows unsymmetrical aerodynamic derivatives have obvious effect on transient angular motion of spinning vehicle, thus the angular motion behaviour cannot be modeled accurately with symmetrical stability derivative characteristic. The similar effect on peak-valley value and phase of total angle of attack curve are also discussed. Anyway, the effect of axisymmetric spinning vehicle unsymmetrical aerodynamic derivative cannot be neglected.