A synthesis method of labeling histone deacetylase inhibitor (HDAC inhibitors) SC027 with Gallium-67 or Gallium-68 radionuclide, wherein a labeled precursor DOTA-SC027 which comprises DOTA-NHS-ester (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-N-hydroxysuccinimide-ester) and HDACi-SC027 is prepared for the synthesis to label HDACi-SC027 with Gallium-67 or Gallium-68 radionuclide for producing imaging tracers for tracking the HDACi.