Based on Parratt’s formula

the algorithms of rough interface multilayer reflectivity and the resolution of scattering vector Q in the neutron reflection experiment are discussed. The differences and the use conditions have been described of the exponent method and the lames method

which are two algorithms to deal with the roughness of interfaces. Combined with experimental data of polarized neutron TOF reflection

the two fitting methods have been compared. The results indicate that the split lames algorithm of reflectivity is more suitable for the model in which interfacial roughness is in the order of thickness. As for resolution

the convolution considering angle or wavelength resolution is better than the convolution considering scattering vector.