On the basis of the biological equivalent theory，the control variable method is used to measure the elec-trocardiograms (ECGs) of testees under low-illumination LED lights with different colors and to explore the corre-sponding non-visual biological effect on human body’s physiological function． The results show that low-illumina-tion light source has certain effect on human electrocardiograms; and that the wavelength of low-illumination light source influences human ECG parameters． For instance，blue light significantly speeds up human heart rate while red and green lights have relatively greater effect on the depolarization and repolarization of the ventricle． Moreover，it is also found that both the depolarization time and the repolarization time increase under the illumination of these three kinds of light sources．