Based on features of dimension variation propagation in multi-station assembly processes, a new quality evaluation model of assembly processes is established. Firstly, the error source of multi-station assembly system is analyzed, the relationship of dimension variation propagation in multi-station assembly processes is studied and the state equation for variation propagation is constructed too. Then, the feature parameters which influence variation propagation and accumulation in multi-station assembly processes are found to evaluate quality characteristic of the assembly system. Through the derivation of equation on dimension variation propagation, station coefficient matrices which are combined and conversed to determine the max eigenvalue are educed. The max eigenvalue is multiplied by the weight coefficient to establish the quality evaluation model in multi-station assembly processes. Furthermore, assembly variation indexes are proposed to judge of the assembly technology process. Finally, through the practical example, the application of the model and assembly variation indexes are presented.