An early-warning method by means of a wind power generator gearbox early-warning device relates to a monitoring system, and particularly to wind power generator gearbox early-warning technology. The early-warning method settles a problem of low adaptability caused by high complexity and high variability of a wind power generator set operation working condition. According to the early-warning method, when duration time of wind speed in one wind speed interval reaches an upper time limit or the lubricant temperature in the wind speed interval reaches a lubricant temperature early-warning value, a main controller of a control unit transmits a warning signal to a server through a wireless communication circuit, thereby realizing early-warning for a wind power generator gearbox. When the continuous vibration accelerating time of the gearbox in a random vibration acceleration reaches an upper duration time value, the main controller of the control unit transmits the warning signal to the server through the wireless communication circuit, thereby realizing early-warning for the wind power generator gearbox. The early-warning method is suitable for performing early warning on the wind power generator gearbox.