The temperature dependent saturation magnetization curve of amorphous Fe₇₆Co₁₈B₁₄Si₁, alloy was measured using a SQUID magnetometer and vibrating sample magnetometer from 5 K up to 800 K. Inelastic neutron neutron scattering measurements also have been used to study the long wavelength spin dynamics of this high T_c amorphous ferromagnetic alloy. The magnon dispersion curve exhibit the conventional quadratic relationship E = D (T) q² + △, typical of an isotropic ferromagnet. An estimate of the T=0 value of spin wave stiffness constant, D (0) ≃ 144mVÅ value was obtained from a low temperature magnetization curve, which was consistent with the value obtained from the analysis of inelastic neutron scattering data after consideration of its temperature dependence.