The present disclosure relates to a ranging method and a ranging system, the ranging method includes using a first laser emitting portion of a laser emitting device to emit a vertical laser beam rotating in a vertical plane at a first rotation speed; calculating a time difference between the vertical laser beam passing through a first optical detection component and a second optical detection component by using the first optical detection component and the second optical detection component on a laser receiving device at least partially on the same vertical plane, wherein a distance between the two optical detection components is a first spacing; and calculating a first distance between the laser emitting device and the laser receiving device based on the first rotation speed, the first spacing, and the time difference.