The invention provides a low-dose CT image denoising method and device. The method comprises the following steps: obtaining a plurality of training image groups, wherein each training image group comprises a low-dose CT image and a high-dose CT image; obtaining at least one training image block group from each training image group, and enabling all of the obtained training image block groups to form a training data set, wherein each training image block group comprises a first target image block selected from the low-dose CT image and a second target image block selected from the high-dose CT image and same with the first target image block in position and size; constructing a deep learning network, training the deep learning network by utilizing the training image block groups in the training data set and obtaining a denoising model; and segmenting an image to be denoised into a plurality of image blocks, inputting each image block into the denoising model for denoising, and splicing the image blocks obtained after denoising to obtain a denoised low-dose CT image. The denoising method has a better de-noising effect and robustness.