Cyanate ester resin (CER) is an excellent thermal stable polymer. However, its mechanical properties are not appropriate for its application, with brittle weakness, and it has poor functional properties, such as luminescence. This work innovatively combines the luminescence property and the improved mechanical properties with the inherent thermal property of cyanate ester. A novel nanocomposite, CER/uMWCNTs/Eu, with multi-functional properties, has been prepared. The results show that with the addition of 0.1 wt.% of uMWCNTs to the resin, the flexural strength and tensile strength increased 59.3% and 49.3%, respectively. As the curing process of the CER progresses, the injected luminescence signal becomes luminescence behind the visible (FBV). The luminescence intensity of CER/uMWCNTs/Eu was much stronger than that of CER/MWCNTs/Eu, and the luminescence lifetime of CER/MWCNTs/Eu and CER/uMWCNTs/Eu was 8.61 μs and 186.39 μs, respectively. FBV exhibited great potential in the embedment of photon quantum information. Therefore, it can be predicted that CER/uMWCNTs/Eu composites will not only have a wide range of applications in sensing, detection, and other aspects, but will also exhibit great potential in the embedding of photon quantum information.