A 2D layer Cu(II) coordination polymer [Cu(npth)(H₂O)]_n (1) was crystallized from a mixture of 3-nitrophthalic acid and Cu(OAc)₂·H₂O in water under room temperature and structurally characterized by single-crystal X-ray diffraction, FT-IR and TGA. Compound 1 was applied to make a nanocomposite with graphene oxide (GO). A highly dispersible and stable nanocomposite of Cu(npth)-GO was successfully synthesized by a simple ultrasonication method. SEM, TEM, UV-vis, FT-IR and TGA were used to characterize the morphology and structure of the prepared composite. In accordance with the characterization results, we suspected that the binding mechanism of Cu(npth) and GO was assigned to be the cooperative interaction of Cu–O coordination, π-π stacking and hydrogen bonding.