The glass-forming tendency and specific heat in ice cold water-quenched Ge1−xSnxSe2.5 glassy alloys with 0<x<0.6 were investigated by means of differential scanning calorimetry. The heat of fusion ΔHf, the heat ΔHc associated with the crystallization of an amorphous phase and the glass transition temperatureTg were deduced from the DSC curves. The composition dependence of glass forming ability,Tg and crystallization behavior has been discussed.