Abstract. In order to understand the monopole interaction effect on the single particle energies and the shell evolution, we have studied Z=51 isotopes with odd mass number in the vicinity of 132Sn mass region. We have performed some spectroscopic calculations in the framework of nuclear shell model using kh5082 and mkh effective interactions in a truncated space, which is constructed taking into account the evolution of the effective single particle energies in the studied mass region.Keywords: Monopole interaction, Shell Evolution, Nuclear structure, Odd A Antimony isotopes, Oxbash code