Abstract: The effects of light, temperature, pH, oxidant, anti-oxidant, metal ions, saccharides on stabilities of ascorbic acid (AA) and ascorbyl palmitate (AP) were studied. Results showed that they were destroyed by sunlight, high temperature, oxidant in different extent and sensitive in neutral and alkaline conditions and AP was more stable than AA. Vitamin E (VE) could protect AP effectively. Cu2+, Fe3+ and Mn2+ could lead to large loss of AA, Mn2+ had obvious effect on AP. They were stable when glucose and sucrose existed.