In this paper, we derive the virtual structure constants used in the mirror computation of the degree k hypersurface in CPN-1, by using a localization computation applied to moduli space of polynomial maps from CP1 to CPN-1 with two marked points. This moduli space corresponds to the GIT quotient of the standard moduli space of instantons of Gauged Linear Sigma Model by the standard torus action. We also apply this technique to the non-nef local geometry
and realize the mirror computation without using Birkhoff factorization. Especially, we obtain a geometrical construction of the expansion coefficients of the mirror maps of these models.