The proportion of red and blue lights of the LED lamp we used for the supplementary lighting experiment on tomato seedlings is 4:1. First, we slected some tomato seeds and sowed them into the soil in the plastic pots. The green plant pot is used as the experimental group A which carries out the light supplementary experiment. And the white plant pot is taken as the comparison group B which just uses the sunlight for photosynthesis. Equal amounts of water and manure were put into the pot A and B in the period of the experiment. We used the plant light supplementary system to provide light for the seedings in group A during night and during the daytime both of group A and B receiving the sunlight. So the seedings in group B wre not be supplemented extra light radiation except the sunlight. We had an observation and record for more than a month and the comparison result is very obvious. The tomato seedings in group A that carried out light supplementary experiment grouped taller and stronger than the group B. Fig. 10 is the photograph of the LED Supplementary Lighting System. Fig. 11 is the comparison of the tomato seedings’ growth situation of the two groups A and B after fifteen days. Fig. 12 is the comparison of the grouth situation of groups A and B for thirty days. Fig. 13 is the effect picture of the LED supplementary lighting system at the thirtieth day.