The invention discloses an excessive noxious gas early warning method and an excessive noxious gas early warning system based on a wearable device. The method is characterized in that excessive noxious gas alarming information comprising position information uploaded by the wearable device can be received; the excessive noxious gas early warning area information comprising the position area information can be generated according to the excessive noxious gas alarming information; current position information transmitted by the wearable device can be received; whether the current position information belongs to the position area of the excessive noxious gas early warning area information can be determined; the early warning information can be transmitted to the wearable device, or the wearable device and the intelligent terminal corresponding to the wearable device. When the current position information transmitted by the wearable device belongs to the position area of the excessive noxious gas early warning area information, the early warning information can be sent to the wearable device, or the wearable device and the intelligent terminal corresponding to the wearable device, and then the user can be aware of the areas full of the noxious gas, and can avoid going to the areas.