The firing tests with clay blocks were undertaken to study the fluorine expulsion and retention characteristics of calcium-based materials during the firing of brick clays. The results indicate that fluorine expulsion begins at approx. 600-700degreesC, and the main portion occurs in 800-1000degreesC. The mode of firing has some effects on fluorine expulsion. Additives of calcium-based material can reduce fluorine expulsion, which is mainly attributed to the increased formation of CaF2 during clay firing, In addition, the optimum addition tests of 6 calcium-based materials with higher efficiency were carried out in a brick kiln. More than 75% fluorine is retained in the brick body and there is no adverse effect on brick product. This makes it possible for brickyard to achieve non-polluting production.