A new moss species, Didymodon daqingii J. Kou, R.H. Zander & C. Feng (Pottiaceae) from the Daqing Mountains in semi-arid region in Inner Mongolia, China is described and illustrated. It is characterized by long-lanceolate leaves that are appressedincurved when dry; subulate, very fragile and bistratose leaf apices; abruptly broadened and rounded leaf bases; distally bistratose leaf margins that are recurved in proximal 1/2–3/4; long-excurrent costa with guide cells in 2–3 layers; papillose distal laminal cells, and yellow-green KOH laminal color reaction. Following recent Zander's revisionary work of the genus Didymodon s. lato, D. daqingii belongs in the emended genus Didymodon s. stricto. It is compared with morphologically similar species and its habitat ecology is discussed.