Abstract: In the course of the oval incubation and larvae of fish separately treatingwith the low-dose neutron irradiation. It is proved that can accelerate the ovalincubation time, and have a promotive action to fish growth. At the initial stageof sexual gland development and silkon seed, the neutron irradiation also have thesame effect. This unit is composed of ~(241)Am-Be neutron source and irradiationcavity and automatic control system, etc. At the different development time offish growth, we have operated this unit to irradiate the oval of carp and clariasfuscus taking the definite neutron flux and initially obtained the obvious effect onincrease output.