Numerical aperture (NA) of the projection objectives of the immersion microlithographic projection exposure machines has reached 1.35 and the measurements of the illumination pupil should meet very stringent requirements. A Fourier transform lens is designed and used for the measurement of the illumination pupil of the immersion microlithographic projection exposure machines. It is analyzed that the distortion of the Fourier transform lens should be negative, and the threshold of the deviation from the sine condition (DSC) of the Fourier transform lens is also analyzed on condition of the actual requirement of the illumination pupil measurement. The design method is that the different negative distortions are set on the different field of view (FOV) positions. We has worked out a Fourier transform lens with five elements and one kind of optical material and it meets the requirements of the DSC, wave front error, modulcotion transfer function (MTF) and distortion for the illumination pupil measurements of the immersion microlithographic projection exposure machines. It is also analyzed when the Fourier transform lens is used at inverse direction. It is confirmed that the design method that the different negative distortions are set on the different FOV positions of the Fourier transform lens is valid.