  The Large Sky Area Multi--object Fibre Spectroscopic Telescope (LAMOST) is
the largest (aperture 4 m) wide field of view (FOV) telescope and is equipped
with the largest amount (4000) of optical fibres in the world. For the LAMOST
North and the LAMOST South the FOV are 5 deg and 3.5 deg, the linear diameters
are 1.75 m and 1.22 m, respectively. A new kind of atmospheric dispersion
corrector (ADC) is put forward and designed for LAMOST. It is a segmented lens
which consists of many lens--prism strips. Although it is very big, its
thickness is only 12 mm. Thus the difficulty of obtaining big optical glass is
avoided, and the aberration caused by the ADC is small. Moving this segmented
lens along the optical axis, the different dispersions can be obtained. The
effects of ADC's slits on the diffraction energy distribution and on the
obstruction of light are discussed. The aberration caused by ADC is calculated
and discussed. All these results are acceptable. Such an ADC could also be used
for other optical fibre spectroscopic telescopes, especially those which a have
very large FOV.
