  In this paper we interpret the hidden symmetry of the moduli space of IIB
superstring on $AdS_{5}\times S^{5}$ in terms of the chiral embedding in
$AdS_{5}$, which turns to be the $\mathbb{CP}^{3}$ conformal affine Toda model.
We review how the position $\mu $ of poles in the Riemann-Hilbert formulation
of dressing transformation and how the value of loop parameters $\mu $ in the
vertex operator of affine algebra determines the moduli space of the soliton
solutions, which describes the moduli space of the Green-Schwarz superstring.
We show also how this affine SU(4) symmetry affinize the conformal symmetry in
the twistor space, and how a soliton string corresponds to a Robinson
congruence with twist and dilation spin coefficients $\mu $ of twistor.
