The electroforming replication process has been widely used in the fabrication of nested x-ray telescopes. The imaging performance of the mirrors is determined largely by the shape accuracy of the mandrels. To predict the imaging performance of mirrors replicated from mandrels with different parameter and fabrication errors, a special Monte Carlo ray tracing model is established and verified by experiments. Then, based on ray tracing numerical calculation, the influence of each major fabrication error is discussed. Furthermore, according to the results obtained by the simulation of slope error, a method for evaluating the relationship between the mandrel full-band errors and imaging quality is proposed and then verified by experiments. The results show that the power spectral density (PSD) reference given by the method can well reflect the quality of the mandrels, and guide the fabrication process. (C) 2022 Optica Publishing Group