A new species Diorygma tiantaiense Z.F. Jia, sp. nov. was found, which is characterized by a corticolous thallus with norstictic acid, oval or oblong apothecia, immersed to ± raised discs with white pruina, and large muriform ascospores (120–210 × 35–60 µm). Detailed morphological descriptions, photographs, and a comparison and discussion of similar species are provided. A checklist and key to the species of Diorygma known from China is presented. Keywords: lichenized fungi; lecanoromycetes; graphidales; graphidaceae; taxonomy.