Avionics networks work in a real-time manner where the intended functions should be performed before time deadline. To assess the reliability of an avionic network comprehensively, the metric delay as well as the common-cause failures are taken into consideration and a task-based model with delay constraints is built. Moreover, an efficient ordered binary decision diagram (OBDD) based approach, named time-constraint edge expansion, is proposed which incorporates delay constraints into the edge expansion diagram to construct OBDD and analyzes network reliability with common-cause failures on the basis of the original OBDD. A sample network is shown to illustrate the evaluation procedure using the proposed approach. The experiment results verify the correctness and efficiency of the approach in reliability analysis for avionics networks.