Artifact reduction method and apparatus, and image processing method and apparatus are provided. The artifact reduction apparatus includes a scaling-down unit, a buffer unit, an artifact detection unit, a scaling-up unit and a filter unit. The scaling-down unit scales down a resolution of a current original image frame to obtain a current low-resolution image frame. The artifact detection unit performs an artifact detection to the current low-resolution image frame to obtain low-resolution weights in accordance with a relation of the current low-resolution image frame and a previous low-resolution image frame provided by the buffer unit. The scaling-up unit scales up a number of the low-resolution weights to obtain a high-resolution weights. By using the high-resolution weights, the filter unit performs an image processing procedure to the current original image frame for reducing artifact of the current original image frame and obtaining an adjusted image frame.