A dynamic similarity scaled aircraft model was tested in spin tunnel to investigate spin characteristics of a large civil aircraft in first time. The spin characteristic of aircraft model was investigated based on kinematic parameters which was recorded by sensors. The research on aerodynamic moment which acts on the aircraft model in spin motion is still very absent. Base on results of the large civil aircraft model freespin test, aerodynamic moments were calculated by six degree freedom equation of motion, reliability of calculated results were validated by the comparison with results of force measurement of aircraft model in normal wind tunnel in this paper. Finally, system identification research of aircraft model spin motion was carried out, multivariate polynomial equation was used. The mathematical model which can be used to identify the moment coefficients was created, several important aerodynamic derivative was identified, such as Cmα,Cmδe,Cmq,Cnβ,Cnδr,Cnr,Clβ,Clδr,Clp.These derivatives were validated by the reference value.