Blue-emitting room-temperature phosphorescence (RTP) materials have always been one of the major challenges in the field of RTP materials. Deep-blue (430 nm) RTP emitting silica microparticles were prepared via a one-step hydrothermal reaction from a single raw material of 3-aminopropyltriethoxysilane (APTES). APTES provided amino groups and ethyl groups as a nitrogen and carbon source, which was further condensed to be nitrogen-contained carbon dots (CDs). Besides, the siloxane side of APTES was hydrolyzed and formed silica microparticles. The CDs with the potential chromophores (C═O and C-N etc.) were connected to SiO2 via Si-C bonds of APTES. The covalent bonds and the rigid silica network effectively restricted the motions of potential chromophores of the CDs and reduced the energy gap between the singlet state and triplet state, which was favorable to the RTP. It was believed that this work will guide researchers to realize other blue or deep-blue RTP materials.