Abstract: A two dimensional computation model was established by using FEM for unidirectional cord reinforced rubber composites. Given cord fracture and debonding slippage, the transient temperature field of rubber composites was simulated under cyclic loading to determine the effect of cord debonding slip friction on heat generation lag time. Temperature rose dramatically with cord fracture, while debonding slip friction caused a much lower temperature increase. The high temperature range increase caused by local stress concentration with cord fracture is an important factor affecting material failure. These results provide a valuable reference for the design of rubber composites products.