A new phase of RhB4 is predicted based on first-principles calculations.The new phase belongs to the orthorhombic Pnnm space group,named as o-RhB4,and analysis of the calculated enthalpy shows that o-RhB4 belongs to the orthorhombic Pnnm space group.The calculated phonon band structure shows that the orthorhombic Pnnm o-RhB4 structure is stable at ambient pressure.We expect that the phase transition can be further confirmed by experiments.