The present invention discloses an abdominal CT image measuring apparatus and method. The abdominal CT image measuring apparatus includes: an interface unit; a part recognizing unit and a characteristic data computing unit. The present invention can determine the specific region of the part under test with a little amount of computation, by registration and subtraction operation on the two-phase scan images. This is easy to be carried out in computers, thus the computing speed of the characteristic data can be guaranteed and the efficiency can be improved. By the recognizing of the kidney regions and the abdominal aorta region in the present invention, the glomerular filtration rates obtained by applying the key concept of the present invention to the image measuring of glomerular filtration rate can meet the clinical application requirements in both precision and speed.