Thermal change of tin iodide (SnI2) evaporated film as-deposited on a glass substrate has been successfully detected by TG (heating rate, 10-degrees-C/min-1) film mass about 0.5 mg, film area about 2 cm2. A mass loss at 260-420-degrees-C in an argon flow is attributed to the evaporation of SnI2. A mass loss at 180-290-degrees-C in an air flow is interpreted as oxidation of SnI2 to form SnI4 vapor and tin oxide. The TG-DTA for SnI2 and SnI4 powders in a nitrogen flow (heating rate, 10-degrees-C min have been performed to understand the thermal change of SnI2 thin films; an endothermic phenomenon without mass change attributed to melting at 319 and 144-degrees-C and an endothermic mass loss attributed to evaporation at 300-460 and 85-190-degrees-C were observed for SnI2 and SnI4 powders, respectively. A small mass loss (about 7%) at 85-150-degrees-C for SnI2 powders is attributed to the evaporation of SnI4 impurity.