The invention relates to a method and a device for culture medium inoculation by using gravity to control strength. The device comprises a rotary inoculation tray and is characterized in that the rotary inoculation tray is provided with a plurality of inoculation ring mechanisms; each inoculation ring mechanism comprises an inoculation ring and a pin shaft; the inoculation ring penetrates into the pin shaft; the pin shaft is fixed in a fixed base of the inoculation ring; the fixed base of the inoculation ring is fixed on the rotary inoculation tray. The device disclosed by the invention is compact in structure, has the functions of sampling, inoculation and sterilization and has the main characteristics that the inoculation ring adopts a gravity method, an inoculation end of the inoculation ring is attached to the surface of a culture medium by eccentric weight of the inoculation ring, the culture medium is not damaged and failed inoculation of the culture medium is prevented, so the device provides a brand-new automatic inoculation method.