To improve the signal -to-noise ratio of on -line boron concentration measuring device , we have analyzed the three factors of neutron interference counting , neutron scattering and neutron moderator impact on Signal to Noise Ratio ( SNR) , and put forward some measures , such as using cadmium plate that can improve the SNR.And the results from experiment and MCNP simulation demonstrate that these measures are very effec -tive and will enabl...