Two kinds of 1 W white high power light emitting diode (LED) were made by packaging blue chips from Taiwan and US. The chips were coated by the same phosphor and transparent silica gel. Optical properties of the two kinds of LEDs were investigated in the temperature range of 15-75 degrees C and at the current of 350 mA. The results show that temperature badly affects the optical parameters such as peak wavelength, radiant flux, color temperature and so on. After analyzing the PL spectrum, the relationship between temperature and LED performance was found. The reasons for optical parameters vs. temperature were theoretically analyzed. Some suggestions were given to reduce the influence of temperature on power LED.