Aiming at the mechanical system related to multi-component failure， a reliability evaluation method of multi-component system based on time-varying Copula function was proposed. Firstly， the nonlinear Wiener process was introduced to characterize the performance degradation process， and the Copula function was used to characterize the correlation between multiple component failures. Secondly， based on the evolutionary equation of the Copula function approximation of the Fourier series， the fitting effects of the Fourier series on common time-varying forms were verified by Monte Carlo （MC） simulation. In addition， the likelihood ratio statistic was used to test the existence of time-varying correlation， indicating the necessity of time-varying correlation research. The example analysis shows that compared with the static correlation model， the time-varying correlation model has the log-likelihood function value increased by 4.36%， and the Akaike Information Criterion （AIC） decreased by 3.81%， achieving more accurate reliability evaluation results.

In the reliability evaluation of many high-reliability and high-value products， product reliability often cannot be accurately evaluated due to the lack of objective test data. Aiming at this problem， a reliability evaluation method for high-reliability products based on improved evidence fusion was proposed in order to make full use of reliability information from different sources. Firstly， combining the characteristics of reliability engineering， the modified weight of each evidence was determined by the consistency of the evidence at credal level， pignistic level and the uncertainty of the evidence itself. Secondly， the optimal comprehensive weight was obtained by linear combination of each weight vector based on game theory. Finally， the Dempster’s combination rule was used to fuse the modified evidence， and the probability distribution of the product reliability index was obtained through the Pignistic probability transformation formula to complete the product reliability evaluation. The reliability evaluation results of one electronic device show that compared with the results of Jiang’s combination method and Yang’s combination method， which also consider multi-dimensional weight modification， the credibility of the conflict interval given by the proposed method is reduced by 69.6% and 54.6% respectively， and the credibility of the overall frame of discrimination given by the proposed method is reduced by 5.6% and 3.7% respectively. Therefore， in the application of reliability engineering， the performance of the proposed method in solving evidence conflict and reducing the uncertainty of fusion results is better than that of the comparison methods， and this method can fuse multi-source reliability information effectively and improve the credibility of the results of product reliability evaluation.