Abstract: Based on the assumption that there is a neutron and γ radiation field with single and pulsed and high γ/n ratio, and the time spectrum FWHM is about 10 ns and several 10 ms, respectively for γ-ray and fusion neutron, it brings forward the detection theory for the above radiation under the current and count mode. Because of the earlier arrival of γ-ray，it reduces the background radiation and is propitious to pick up the signal.