With the uniaxial cyclic loading/unloading test at room temperature, data of the plastic deformation, elastic recovery deformation and inelastic recovery deformation of polycrystalline beryllium samples with different elongation was obtained. Investigation on mathematical characteristics of the inelastic recovery was carried out, and corresponding expression functions were obtained. The result indicates that: after completely unloading, the relationship between inelastic recovery strain and plastic strain of beryllium can be described by the power function; even being incomplete unloading, their relationship can also be described by the power function; all the two function parameters are related to the unloading stress level in analytic form with the square polynomials,and the linear correlativity is presented between the two parameters；in the same unloading cycle, the relationship between inelastic recovery strain and plastic strain can be described by the square polynomials, at least two function parameters show the universal mathematical characteristics beyond specific samples; the modulus of elasticity (also maybe the elongation) is closely relevant to trends of change of all mathematical model parameters..