The invention discloses a screening method for candidate nodules based on CT images and relates to the field of medical image processing. The screening method comprises the following steps: step 1, obtaining a to-be-detected lung CT image f0(x, y); step 2, binarizing the lung CT image f0(x, y) in the step 1 and extracting a lung parenchyma preliminary template f1(x, y); step 3, performing lung parenchyma repair and calculation on the lung parenchyma preliminary template f1 (x, y) to obtain a lung parenchyma region image f2 (x, y); step 4, binarizing the lung parenchyma region image f2(x, y) and screening candidate nodules to obtain a candidate nodule set R; step 5, constructing a 3DCNN network structure for classifying candidate nodules; step 6, training the 3DCNN network model according to the 3DCNN network structure and the library lung CT image in a LIDC lung image database; and step 7, determining the probability of each candidate nodule in the candidate nodule set R being a pulmonary nodule according to the 3DCNN network model.