Introducing the Dyson-Maleev transformation. the coherent state ansatz and the time-dependent variation principle, we obtain two partial different equations of motion from Hamiltonian. Employing the method of multiple scales. we reduce these equations into the envelope function equations and force the amplitude function to satisfy a nonlinear Schrodinger equation. Using the inverse- scat-tering transformation, we obtain the single soliton solution and discuss the solitary magnon localization in antiferromagnet RbFeBr3 The coherent state ansatz and the time-dependent variation principle, we obtain two partial different equations of motion from Hamiltonian. Emplining the method of multiple scales. We reduce these equations into the envelope function equations and force the amplitude function to satisfy a nonlinear Schrodinger equation. using the inverse-scat-tering transformation, we obtain the single soliton solution and discuss the solitary magnon localization in antiferromagnet RbFeBr3