Differential thermal analysis studies on the crystallization kinetics and phase developments of barium strontium titanate glass-ceramics have been performed for a series of glass particles with different particle sizes. The crystallization behavior was deduced to be influenced strongly by the particle size of the glass samples. These studies have revealed the initial formation at lower temperatures of metastable fresnoite Ba2TiSi2O8 (BTS) phase followed by its transformation at higher temperatures to feldspar BaAl2Si2O8 (BAS) and perovskite (Ba,Sr)TiO3 (BST) phases. The metastable BTS phase was proved to crystallize predominately by surface crystallization while the feldspar BAS phase showed significant evidence of internal crystallization. And for the perovskite BST phase, crystallization mechanism changes from surface to internal type at a critical particle size of 75m. In addition, activation energy and the Avrami parameter for crystallization have been determined for the three phases by the employment of glass samples with two typical particle sizes.