The disclosure is related to a chemical structure, a preparation and an imaging method of a tumor imaging tracer, especially to a SPECT radionuclide-labeled trimeric cyclic RGD peptide: 99mTc-4P-RGD3which functions as a ligand to be combined with integrin αvβ3 receptor in tumor for tumor imaging. The preparation includes linking HYNIC-OSu with 4P-RGD3 to form HYNIC-4P-RGD3 and then chelating HYNIC with 99mTc to create 99mTc-4P-RGD3Animal biodistribution and imaging experiments reveal higher uptake in tumor and lower uptake in normal organs, therefore the disclosure can improve image quality, Through animal metabolic experiments, the original form of 99mTc-4P-RGD3 can be still excreted without the evidence of further metabolites in urine and feces. According to the disclosure, the tumor imaging tracer 99mTc-4P-RGD; combined with the integrin αvβ3 solves the issue of high background uptake in normal organs, such that radio-labeled SPECT imaging tracers are more suitable for animal whole-body tumor evaluation.