The purpose of the JSNS$^{2}$ experiment is to search for sterile neutrinos with Δm$^{2}$ near 1eV$^{2}$. A 3 GeV J-PARC proton beam incident on a mercury target produces an intense neutrino beam from muon decay at rest. which oscillate to anti-electron neutrinos. The JSNS$^{2}$ detector is located at 24 m baseline from the target. The detector has a fiducial volume of 17 tons filled with GdLS, that efficiently can detect electron anti-neutrinos via the IBD reaction follow by a gamma signal from the captured neutron on Gd. It is essential to shield gamma background to discern inverse beta decay signals. Lead blocks and iron plates are placed on the floor to reduce this beam related gamma background, which is measured using plastic scintillator. We present the results of a study of the gamma background after shielding and compared it with Monte Carlo simulations.