Effects of annealing on bending properties of composites reinforced with plain glass woven fabrics that were treated with different concentrations of silane coupling agent were investigated in this paper. Bending strength increased by annealing in the specimen treated with lower silane concentration. Higher annealing temperature in a range from 80 degreesC to 150 degreesC led to higher bending strength. Then, the fracture mode changed from a micro-crack type (low strength type) to a branched matrix crack type thigh strength type) by annealing.