The invention discloses an optical thin film characterization method based on a cloud-model quantum evolutionary algorithm (CQEA). The method comprises the following steps that firstly, an initial parameter of the CQEA is input; secondly, a microstructure parameter of an optical thin film is subjected to quantum coding, and an initial quantum population is generated; thirdly, based on a fitting evaluation coefficient of grazing incidence x-ray reflection (GIXR) of the thin film, the adaptability for characterizing a quantum individual of an optical thin film structure is evaluated, and the optimal quantum individual is selected; fourthly, whether the optimal quantum individual meets an optimization criterion or not is judged, if the optimal quantum individual meets the optimization criterion, the optimal optical thin film structure parameter is output, the algorithm is stopped, and otherwise, the algorithm continues; fifthly, the quantum population is updated through one-dimensional cloud complementary mutation and cross; sixthly, the quantum population is further updated by using an elitism preservation strategy, and the third step is executed. The method is suitable for the microstructure characterization of single-layer and multi-layer optical thin films based on the GIXR, and has the advantages of being low in calculation complexity, quick in convergence rate, high in solving precision and the like.