The present invention relates to an image filtering method and a CT (Computed Tomography) system. The image filtering method is configured to filter an image in a parallel manner by use of a multi-core processor, and comprises the following steps: firstly, determining a plurality of computing directions for filtering processing according to the number of the dimension of the image and the predetermined neighborhood range of filtering processing； secondly, according to each of the determined computing directions, for one row of pixels in the image, by taking each pixel in the row as an object pixel, performing by each thread in a plurality of threads predetermined filtering computing between the object pixel and the respective neighborhood pixels of the object pixel in the computing direction, saving the filtering computing results as the filtering results of the object pixels and the respective neighborhood pixels in a cumulative manner； and finally accumulating the filtering results of all the determined computing directions to obtain the image filtering result. Therefore, repeated computations in the current parallel computing can be reduced to greatly accelerate parallel computing for image filtering.
