Preparation of lithium carbonate from spodumene concentrate was carried out by a sodium carbonate autoclave process. The effects of different operation conditions including liquid-to-solid ratio, Na/Li ratio, agitation speed, reaction temperature and reaction time on the lithium carbonate conversion efficiencies were initially investigated. The results show that the conversion efficiency is not less than 94% under the optimal conditions. The purity of the obtained lithium carbonate can reaches up to 99.6%, which is higher than that obtained by sulfuric acid method.