Light-emitting diodes (LEDs) are used in various applications due to their small size, durability and energy efficiency. However, the optical properties of LEDs are more complex than those of in candescent lamps. In order to measure the luminous flux of LEDs with low uncertainty, the equipment used for the measurements needs to be carefully characterized. In this paper, measurement system constructed for luminous flux measuring of LEDs is an integrating sphere system. The integrating sphere designed for measurement of LEDs has ports for LED, photometer head, auxiliary lamp, spectroradiometer, to be equipped with thermoelectric cooler (TEC) and integrating sphere with a diameter d = 1 m and inner sphere is coated with barium sulphate ( BaSO4). The study results show that barium sulphate layer has high average value of reflectivity of about 92.6 percent in the visible light region. Uncertainty for luminous flux measurements related to this system is estimated at 1.78 percent at a confidence level P=95 percent, k = 2, in about 10 to 4000/m for COB LEDs. The results obtained were compared with lIIumia Pro System 500-100 - Labsphere - USA.