Composite sandwich panels possess the characterizations of lightweight and high load-bearing capacity. They also face diverse failure modes, and an in-depth study of their mechanical performance and failure mechanisms is essential to ensure structural safety and applicability. In this paper, three-point bending static and fatigue tests were carried out for the sandwich panels consist of plain weave glass fiber/cyanate fabric laminate and Nomex honeycomb by using a specially designed test fixture to investigate the bending-shear load capacity and fatigue performance of the panel, and observe the fatigue damage and failure phenomena. According to the internal stress states of the sandwich panel, fatigue damage models were established for the face panels subjected to in-plane stresses and the sandwich core subjected to out-of-plane shear. Substituting the honeycomb core by an equivalent solid, the bending panel was discretized by using the solid finite elements. Then the bending fatigue lives of the sandwich panel were predicted by means of finite element analysis and cumulative fatigue damage analysis. The simulated bending fatigue performance of the sandwich panel correlate well with the experimental results. The predicted fatigue lives are a little conservative and acceptable.