The application of curved surface fitting for the disposal of the wavefront aberrations got in the measurement of certain paraboloid and hyperboloid is studied. It is found that,for mid-wavelength deformations with an amplitude of 01λ, results can be obtained with RMS error smaller than 0015λ and 0013λ separately. The existence of a special fitting order which leads to the smallest RMS e rror is affirmed. To find out the special fitting order,we work out two methods which help us get the order's value successfully.