In this paper, we realize the crystal basis B(λ) of the irreducible highest weight module V (λ) of level 1 for U q (A (1) n ) using Nakajima monomials satisfying some conditions. Also, from this monomial realization, we obtain the image of Kashiwara embeddingwhere ι is some infinite sequence from the index set of simple roots. Finally, we give a U q (A (1) n )-crystal isomorphism between Young wall realization and monomial realization, and so we can understand the image of Kashiwara embedding Ψ λ ι : B(λ) → Z ∞ ⊗ R λ using the combinatorics of Young walls.