  The s-enhanced and very metal-poor star CS 30322-023 shows a puzzling
abundance pattern of the neutron-capture elements, i.e. several neutron-capture
elements such as Ba, Pb etc. show enhancement, but other neutron-capture
elements such as Sr, Eu etc. exhibit deficient with respect to iron. The study
to this sample star could make people gain a better understanding of s- and
r-process nucleosynthesis at low metallicity. Using a parametric model, we find
that the abundance pattern of the neutron-capture elements could be best
explained by a star that was polluted by an AGB star and the CS 30322-023
binary system formed in a molecular cloud which had never been polluted by
r-process material. The lack of r-process material also indicates that the AGB
companion cannot have undergone a type-1.5 supernova, and thus must have had an
initial mass below 4.0M$_\odot$, while the strong N overabundance and the
absence of a strong C overabundance indicate that the companion's initial mass
was larger than 2.0M$_\odot$. The smaller s-process component coefficient of
this star illustrates that there is less accreted material of this star from
the AGB companion, and the sample star should be formed in the binary system
with larger initial orbital separation where the accretion-induced collapse
(AIC) mechanism can not work.
