A current-sensitive preamplifier for the mini-size ( such as φ6 mm × 10 mm) 3He neutron detector used for neutronics characteristics measurement of sub-critical reactor is introduced in this paper. It can be connected with the detector by a coaxial shielded cable which length is up to 10m
and it is propitious to neutron flux measurement at a high counting rate. The current-sensitive preamplifier is based on the chip of AD8004. Its concrete circuit
compo- nent selection and performance parameters are presented.