The invention provides an interference avoidance method and a system based on positions in a smart power grid. The method and the system are applied to a cellular system, and a frequency band of a cellular comprises M sub-bands. The method comprises the steps that user equipment is divided into N clusters according to the position of each user equipment; a base station selects N sub-bands from the M sub-bands and assigns to the N clusters according to signal channel quality of the sub-bands; when an interfering source enters the cellular system, and operates in the interfered sub-band, and interference is detected by the user equipment of an interfered area, a first interference information report is adopted and sent to the base station; the base station estimates the interfered area according to the first interference information report; the user equipment preassigned in each cluster adopts a second interference information report which is sent to the base station; and the base station confirms the interfered area according to the first interference information report and the second interference information reports, and reassigns a clean sub-band to the cluster in the interfered area. Therefore, the overhead of reassigning the sub-bands due to the interference is lowered.