Calcium borate used for non-pollution flux of ceramic decoration materials is synthesized by using boric acid and calcium carbonate as raw materials. The effects of reaction temperature, concentration, time, pH value and additive agent on synthesis of calcium borate are studied. The synthesized products are characterized by using DTA, XRD, TEM and SEM. The results show that the better conditions are: synthesis temperature is 80-100°C, the proportion of boric acid and water is0.26 ~ 0.42 to 1(mol), the proportion of calcium carbonate and boric acid is 0.09-0.15 to 1(mol), the pH value is 5 ~ 7, reaction time is 3hs. The synthetic calcium borate is non-crystalline with particle size of 0.1 ~ 0.2 µm, when being calcinated at 300°C, the main crystal phase isCaO·3B2O3·4H2O.