More and more attentions have been focused on the lighting source as it plays an important role to people′s health. The light emitting efficiency of light emitting diode has been broken through year by year and now it has been surpassed that of the traditional lighting source. In order to improve the lighting quality by a lighting source with flexible color temperature, a data base is created with different color temperature by mixing different proportion luminous flux of red, green and blue light emitting diode based on theoretical calculations. The data base is embedded into the control program and it can run different proportion to realize light source variation with color temperature at different time. The experimental results show that the lighting source can realize correlated color temperature from 2300~7000 K, real color temperature is in accordance with that of theoretical calculation. Thus a sunlight-style lighting device is realized fundamentally.