Abstract: The present disclosure relates to the technical field of image processing and provides a motion estimation method and apparatus for a tumor, a terminal device, and a storage medium. The method includes: obtaining a current value of a respiratory correlation signal of a patient, the respiratory correlation signal reflecting a motion trajectory feature of a designated organ with the tumor of the patient in each of different respiratory states; inputting the current value of the respiratory correlation signal into a tumor motion estimation model to obtain an estimated current position of the tumor; and inputting the estimated current position of the tumor into an organ motion estimation model to obtain an estimated current velocity vector field of the designated organ. By adopting the motion estimation method, it realizes a respiratory motion estimation for the whole organ and enhance accuracy of positioning the tumor and vital anatomical structures around the tumor.