(-)Epigallocatechin gallate (EGCG), the higest phytochemical compound contained from tea leaf (Camellia sinensis), has been proven to improve blood flow, prevent cardiovascular disease, and eliminate various toxins, improving resistance to various diseases, by its anti-oxidant activity. Green tea catechins especially EGCG can undergo degradation and epimerization during storage conditions. Many factors could contribute to the stability of green tea catechins, including EGCG, such as temperature and duration of storage. The research focused on studying the duration stability of EGCG during storage in low temperature (8°C) using HPLC. HPLC conditions were as follows: C-18 reversed-phase μbondapak 10 urn, 3.9 × 300 mm used as the column, the mobile phase was methanol: water: acetic acid (2%) (30: 65: 5 v/v/v), the flow rate of 1.0 ml/min, and detection monitored at 276.0 nm with spectrophotometry UV-Vis. The levels of EGCG during 32 hours of storage using the refrigerator in 8°C decreased by 20.11%, and the levels of EGCG in 25°C decreased by 26,73%. It was proven that there were significant differences between the level decrease of EGCG in green tea instant beverage products in the refrigerator (8°C) and storage at 25°C.