Upconversion luminescence (UCL) is a process during which low-energy light was converted (excitation) to high-energy light.Due to the characteristics of low excitation power density,negligible autofluorescence,lack of photobleaching and high stability,UCL has been increasingly applied for bioimaging.Using the upconversion nanoparticles (UCNP) as agents in multimodality molecular imaging (UCL imaging,CT,MR,PET,etc),we could obtain clearimages with high signal to noise ratio.This review summarizes the applications of UCNP in the field of bioimaging.