The invention discloses a unified model-based generator excitation system aggregation method. The method comprises the following steps of 1, putting forward a selection principle for an aggregated excitation system model; 2, constructing a unified structure model according to an excitation system state vector coefficient matrix; 3, directly obtaining parameters of an excitation system by utilizing constrained relationships of structural similarity between an equivalent machine model coefficient matrix and a unified model block diagonal matrix and electrical characteristic similarity before and after equivalence. Compared with a method based on frequency domain transfer function fitting and time domain simulation optimization, the method has the advantages that the method does not depend on working point setting or optimizing direction selection, is a time domain non-iterative aggregation parameter analysis and solution method and is particularly suitable for an actual large power grid comprising various excitation models, calculation can be effectively simplified and the equivalent precision is improved; the calculated amount is small, the equivalent precision is high, the excitation models and the parameters can be obtained without iteration, and the method is suitable for aggregation of complicated cluster comprising various excitation models.