The invention relates to a method for compensating missing data in CT (Computed Tomography) scanning, comprising the following steps: according to incorrect or missing projection data information, correcting the incorrect or missing projection data successively with an opposite projection interpolation method, an adjacent projection interpolation method and an interpolation result weighted sum method so as to obtain correct projection data, wherein a weight function is calculated by the interpolation result weighted sum via the following constraint, and f(x) represents the continuous form of the weight: 1) f(x) is continuously differentiable on [0,pi/2]; 2) f(0)=1; 3) lim f(x) is equal to 0; and 4) f(x) is monotonic decreasing in a definitional domain, wherein x is the taper angle of each layer of a CT scanner. The method disclosed by the invention combines the advantages of the opposite projection interpolation and the adjacent projection interpolation, so that when scanning fails, an ideal correction effect can be obtained by using a big taper angle scanner or a small taper angle scanner, and a correct CT image can be reconstructed.