The absolute testing method can be used to test the freeform lens. There are some spatial frequencies terms can’t be getting by the traditional absolute testing method such as even and odd functions method, rotation shear method, rotated equally spaced position method. In this paper we will show the losing terms in the traditional method. In this paper the freeform surface is created by 300th Zernike polynomials. The freeform lens is based on the flat lens. We use the Zernike polynomial to simulate the two flats and use the freeform surface as the three flat. According to the three flat absolute testing methods, we can simulate the testing result. The freeform flat which we use is polishing by the ion figuring machine of NTG.