The aircraft has the characteristics of many parts, complicated structure and high assembly accuracy requirements, and its assembly has requirements for safety assembly and less reversible assembly and so on. Based on the key product characteristics (KPC) and key control characteristics (KCC) parameters of aircraft, a theoretical method for assembly error sensitivity quantification analysis based on the state space model was proposed. And the error sensitivities in the precision assembly process of the buttedjoint assembly of the aircraft were elaborated and defined, which were divided into three levels: feature level, position level and system level. The relationship between input vector and input matrix was obtained by solving the state space model of aircraft and its output equation, and the state transition matrix was obtained, and then the theoretical expressions of different levels of error sensitivity were obtained. The random assembly feature error value which obeys normal distribution was substituted into system matrix. Monte Carlo simulation was used to calculate the sensitivity indexes of different assembly features. And the sensitivity indexes of feature level obtained by theoretical calculation and Monte Carlo simulation respectively were compared and analyzed. The results showed that it was feasible to apply the sensitivity analysis method of dynamic system to the accuracy prediction and analysis of the buttedjoint assembly of the aircraft. The analysis method of aircraft assembly error sensitivity analysis based on state space model proposed was accurate and reasonable. This research method had positive significance for the accuracy evaluation of the buttedjoint precise assembly process of the aircraft.