DSC measurements have been carried out for the as-quenched xNa2O- (15-x)Li2O-4B2O3-11Al2O3-5BaO-65P2O5 (x=0,3.75,7.5,11.25 and 15 mol%) glasses with different particle size. Two crystallization peaks appear on the DSC curves for sample sized 90-110μm. The presence of two crystallization peaks is due to different crystallization mechanisms, surface and bulk (internal) crystallization. The X-ray diffraction measurements are also employed to investigate the crystallization of glasses. The results show that bulk crystallization is difficult to occur in the studied phosphate glasses. The effect of mixed alkali on glass thermal stability is also studied in this paper. The surface and bulk crystallization active energies are calculated according to Kissinger equation.