A model is given out for computing energy coupling coefficient in the process of laser ablating glass fiber/expoxy composites. By the simulation of laser irradiating glass fiber/expoxy composites, laser transmission and the front surface temperature are abtained in the ablation process, which agree well with the experimental results. The result indicates that energy coupling coefficient in the process of laser irradiating glass fiber/expoxy composites can be computed by the proposed model. Besides, the change law of energy coupling coefficient with different laser intensities is computed with the proposed model. The computed result indicates that laser energy absorption mechanism changes from bulk absorption to surface absorption. More intensive laser beam causes that energy coupling coefficient increases more quickly and the conversion process from bulk absorption to surface absorption is faster.