Nanoscale coordination polymers (NCPs) are attracting increasing research interest due to their highly tailorable structure, feasible functionality and promising application in various fields, especially in biomedical applications, they are excellent contrast agents for bioimaging, biosensing and clinical diagnosis. Currently, to overcome the low relaxation rate and unitary information of magnetic resonance imaging, the design of multifunction contrast agent is critical and challenging. Herein, a new Au nanoparticles/Gd-based coordination polymer (Au@GdCP) composite nanoparticles have been fabricated by a facile hydrothermal methodology. The Au@GdCP exhibit excellent magnetic resonance, bright upconversion luminescence (UC) and good biocompatibility. More importantly, with the introduction of Au nanoparticles, the magnetization and longitudinal relaxation rate (r1) of the nanocomposite is enhanced significantly, with 131.6-fold from 5.19 emu/g to 683.52 emu/g and 11.5 fold from 0.248 mM–1S–1 to 2.853 mM–1S–1 enhancement, respectively, as well as better UC property over GdCPs. This work may offer a new way to develop multifunctional NCPs with enhanced performance in image-guided diagnosis and therapy.