Leaching process of B from calcined boron concentrate in NaHCO3 solution was studied. The effects of mass ratio of liquid to solid, sodium bicarbonate consumption, reaction temperature, time and stirring speed on leaching of boron were examined. The results showed that under the optimum conditions of mass ratio of liquid to solid of 2.1:1, sodium bicarbonate consumption of theoretical amount of 150%, leaching temperature of 100℃, leaching time of 1 h, stirring speed of 400 r/min, leaching rate of B reached 92.88%. The morphology of calcined boron concentrate is mainly columnar and flat crystal, which is attached with some small particles. The boron sludge is a lot of little crystals that stack together, and the particle size of boron sludge is smaller. Therefore, it is speculated that leaching process of B from calcined boron concentrate in NaHCO3 solution can be described by the shrinking core model. The major phases in the calcined boron concentrate were suanite, lizardite, phlogopite and olivine, and with the suanite phase disappearing, the major phases in the boron sludge were MgCO3 and Na2Mg(CO3)2.