Abstract: The reaction system and basic characteristic of low- temperature TTI( time- temperature indicator) was determined.The TTI was based on the color change of p H indicator resulted from the hydrolysis of triacetin by alkaline lipase.Finally,parameters of 25 m L reaction system was determined: 5 m L triacetin∶ 20 g / L polyvinyl alcohol emulsion( v∶ v = 1∶ 19,10000 r / min,every time 3 min,5 min intervals,a total of 2 times),19.50 m L 0.05 mol / L p H10.60Gly- Na OH buffer,0.05 m L 1 g / L alkaline lipase,0.25 m L 0.10 mol / L CaCl_2 solution,0.20 m L Thymol blue-phenolphthalein- thymolphthalein mixture indicator.The activation energy of TTI was determined to be 60.14 k J / mol by measuring p H descending rate at different temperature.The TTI can be applied to monitor enzyme reaction or steatolysis of low- temperature food,and further to indicate the quality of corresponding food.