A process of biooxidation followed by thiosulfate leaching of gold from refractory gold concentrate was investigated. Mineralogical studies on the concentrate showed that very fine gold grains (<10 μm) were encapsulated in pyrite and arsenopyrite, while the proportion of monomer gold was only 21％. The gold-bearing sample was identified as a high-sulfur fine-sized wrapped-type refractory gold concentrate. The gold leaching efficiency obtained by direct cyanidation was only 59.86％. After biooxidation pretreatment, the sulfide minerals were al-most completely decomposed, 92wt％ of the mineral particles of the biooxidation residue were decreased to <38 μm, and the proportion of monomer gold in the biooxidation residue was over 86％. Meanwhile, the gold content in the biooxidation residue was enriched to 55.60 g/t, and the S, Fe, and As contents were reduced to approximately 19.8wt％, 6.97wt％, and 0.13wt％, respectively. Ammoniacal thiosulfate was used for gold extraction from the biooxidation residue of the refractory gold concentrate. The results showed that the optimal reagent condi-tions were 0.18 M thiosulfate, 0.02 M copper(II), 1.0 M ammonia, and 0.24 M sulfite. Under these conditions, a maximum gold leaching effi-ciency of 85.05％ was obtained.