In thunderstorm weather, when charged clouds appear over tall buildings, lightning rods and high-rise tops are sensitive to a large amount of charge, because the lightning rod needle is pointed, so when the electrostatic induction, the conductor tip always gathers the most charge. In this way, the lightning rod gathers most of the charge. The lightning rod also forms a capacitor with these charged clouds, because it is more pointed, that is, the capacitor's bipolar plates on the area is very small, the capacitor is very small, that is, it can accommodate very little charge. And it gathers most of the charge, so when there is more charge on the clouds, the air between the lightning rod and the clouds is easily penetrated and becomes a conductor. In this way, the charged cloud and the lightning rod form the path, and the lightning rod is grounded, the lightning rod can import the charge on the cloud into the earth, so that it does not pose a danger to the high-rise building, to ensure its safety.