Image reconstruction method and device for tilted helical scan are provided. The method includes: acquiring data generated by the tilted helical scan; calculating a ray channel parameter and a slice number corresponding to each pixel position based on a geometric relationship that a ray of the tilted helical scan emitting from a ray source to a detector intersects with a pixel; and performing image reconstruction by using a three-dimensional helical back-projection method based on the acquired data, and the ray channel parameter and the slice number corresponding to each pixel position. With the method and device, there is no need to correct the raw data, which ensures the accuracy of the data, and the artifact is avoided, which ensures the accuracy of the reconstructed image.