Rotor–blade parts are the core components of aero-engines

which have the characteristics of complex assembly structure and difficult assembly. Under high temperature and pressure conditions

the rotor-blade assembly error is catalytically amplified

resulting in fatigue cracks and other failures

which seriously affects the stability and reliability of the whole engine. For the rotor-blade structure

traditional variation analysis method cannot comprehensively consider the complex positioning structure and the partial parallel relation

as a result of that a branch chain in the multi-feature parallel structure is often used as a series relationship in a single direction. This paper proposed a variation analysis method of rotor-blade assembly based on the improved Jacobian–Torsor (J–T) model. Firstly

the multi-stage rotational structure

 stop positioning structure and tenon tongue-groove structure were analyzed

and the assembly dimension chain considering partial parallel relationship of the rotor-blade with multi-feature was established. Then the assembly joint surface of rotorblade was expressed as the deviation torsor based on the points contact form by using the incomplete positioning strategy

and a united positioning reference scheme based on the positioning point system was established. Finally

the rotor–blade assembly precision index and the solution method based on the improved J–T model was proposed. Taking the assembly precision analysis for radial

axial and circumferential variation of the rotor-blades as an example

the calculation results of the traditional J–T model

Monte Carlo simulation model

and the improved J–T model were compared with the measured data. The results show that the proposed method has higher prediction accuracy than other methods. Compared with the measured results

the error rate is less than 9%. A more reasonable assembling and connecting mode of tenon tongue-groove structure was put forward