Positron Emission Tomography (PET) is a nuclear medical imaging technique for functional in vivo imaging. In order to image in vivo physiological activities from different aspects, dual-tracer PET approach is further proposed. By injecting two different tracers simultaneously, the radioactive concentration distribution of two tracers can be acquired within one single scan. Nowadays, dual-tracer PET has been applied on the diagnosis and treatments of tumors and neurological diseases. Due to the indistinguishable photon energies emitted from two tracers, dual-tracer PET reconstruction becomes challengeable. PET imaging mechanism, tracers and dual-tracer PET reconstruction are introduced, and the pros and cons of those reconstruction methods are discussed as well. In the end, the possible applications of dual-tracer PET imaging on multi-parameter and multi-mode imaging are prospected.