Two kinds of model, Biological Equivalent model and Circadian Light model which used to evaluate the biological effect of light were discassed and the differences between them were pointed out by fitting curve between the biorhythm factor and human body temperature after several field test. Calculating with the spectrum produced by the LCD screen, it shows that these two models have a stronger restraint of green light band while the red band of light appear not too consistent with the actual results. By tested the forehead temperature under different colors of LED light and fitting with the calculated biorhythm factor, it demonstrates that the forehead temperature increases with the biorhythm factor linearly. And the linear fitting correlation of biological equivalent model is 0.95.