We derive the coherent state representation of the integrable spin chain Hamiltonian with non-compact supersymmetry group G = SU ( 1 , 1 | 1 ) . By passing to the continuous limit, we find a spin chain sigma model describing a string moving on the supercoset G / H , H being the stabilizer group. The action is written in a manifestly G-invariant form in terms of the Cartan forms and the string coordinates in the supercoset. The spin chain sigma model is shown to agree with that following from the Green–Schwarz action describing two-charged string spinning on AdS 5 × S 5 .