Based on the studies of electrochemiluminescence(ECL) of luminol in neutral medium, the iodide would greatly sensitize the ECL of luminol. The ECL luminous intensity responded linearly to the concentration of iodide within the range of 3.8 x 10(-7) mol x L(-1) to 2.2 x 10(-6) mol x L(-1), and the detection limit is 4.0 x 10(-8) mol x L(-1). The mechanism of enhancement effect of iodide on luminol's ECL is also discussed. The experimental results showed that it was a free radical procedure.