Heavy metal pollution from carbonate-type tailings in buffering/neutral mine drainage (NMD) period tends to be ignored. With the tailings of cassiterite-sulfide deposits in the Dachang ore district of Guangxi as the study object, the author conducted column leaching test to investigate the mechanism of heavy metals release from carbonate-type tailings in buffering period, so as to provide the basis for prevention and control of the heavy metal pollution involving the tailings. The results show that there probably exists the pollution of Sb, Zn, Cd, As (Pb) release from Dachangs tailings in the buffer period (about 7 years, with pH value being 6.6~8.0). At the beginning stage of tailings stacking (0 to 0.5 years, with pH value dropped from 7.6 to 7.2), Zn, Sb and Cd are quickly and heavily released; in the middle stage (0.5 to 2.5 years, with pH value fluctuating from 7.2 to 8.0), Sb is more smoothly released; in the late stage (2.5 to 7 years, with pH value changing between 8.0 and 6.6, showing a decreasing trend), As, Sb (Pb) fluctuate periodically or intermittently following air temperature and pH value, implying that when temperature and pH value are high in summer, element concentrations are higher; on the contrary, element concentrations are lower with the lowering temperature and pH value in winter. The heavy metals release is related to the oxidation degree/oxidation sequence of sulfide minerals that the metals are hosted in. The oxidation sequence of these minerals are sphalerite (Zn, Cd), franckeite (Sb)→jamesonite (Sb) →arsenopyrite (As), galena (Pb). Therefore, the measures to prevent and control the heavy metal pollution of the carbonate-type tailings (Dachang, Guangxi) in the buffering period should be carried out targetedly on the basis of tailings stocking stage and season (summer). After the buffer period (7 years), researchers should pay attention to the pollution combining the acid mine drainage (AMD) with heavy metals (As, Sb).